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CleanMail User Manual

1. lt Back Next gt conca Figure 4 4 Anti Virus Filter Setup If your virus scanner is not on the list of supported scanners choose Other on the first page of the setup dialog Consult the virus scanner s documentation to find out command line options and usage instructions For most filters the output of a filter is forwarded to the next filter as its input This can t be applied to most virus checkers because virus checkers analyze a message only signalling yes this is a virus or no this is not a virus with different program exit codes For this reason virus filters are by default configured in a way that the input file is forwarded to the output by leaving the use console output switch unchecked Normally you will want to delete a message if the return code of the filter indicates a virus has been found and deliver a message if not Set the return code policies accordingly When testing a virus filter test it both against the sample virus mail and against the sample spam mail The virus mail must be blocked reject delete with the filter output empty while the spam mail must pass filter output the same as the input Important For security reasons anti virus filters and the attachment blocker by default ignore whitelisting You can change this behaviour by removing the check mark from the Ignore Whitelist setting Note 1 Integrating a virus checker in CleanMail requires that you i
2. Anti Virus Anti Spam Anti Phishing MH byteplant O L 0 2 y Q Q CleanMail Home Version 4 0 Manual Byteplant GmbH August 18 2009 Contents 1 Introduction 1 1 Filtering 0 64044 8 2 5 6 bab dee a ok sz 1 2 SMTP Filtefing rs metres MS MOVERVICW 2 xe ak Seed a ee 0 m na el iia b 2 Installation 2 1 Quick Start Installation Procedure 2 1 1 CleanMail Installation 2 1 2 Configuring Your Email Client for CleanMail 2 2 CleanMail Setup 2 3 Troubleshooting the CleanMail Installation 2 3 1 About Sockets Ports and Listeners 2 3 2 Testing the Basic Proxy Setup 2 3 3 Firewall Configuration 2 4 Registering CleanMail 2 5 Uninstalling CleanMail 2 5 1 Using CleanMail Uninstall 2 5 2 Using The Microsoft Windows Control Panel 3 Concepts 3 1 Proxy Ports ae ek es 3 2 Filter Pipeline ee a a A A A Ed Acera 4 Configuration 4 1 POP3 Proxy Port Setup 4 1 1 POP3 Server and Port Settings 4 1 2 Changing the Mail Account Settings 41 3 Logging Options 4 2 Mail Filter Setup 421 Filter Name su nace x me Ge de da a ea 42 2 Filter Res
3. Do NOT use the character Subject Tag SPAM 5 Next gt Cancel Figure 4 5 SpamAssassin Options Setup 4 9 2 1 Required Score SpamAssassin tests each incoming mail against its spam detection ruleset Each matching rule adds a predefined score to the overall spam score 30 Set the threshold score required for a mail to be considered spam The default setting is 5 0 vvhich is quite aggressive increase this value to reduce the probability of false positives 4 9 2 2 Subject Tag Set the text added to the subject of mails considered spam The keyword _SCORE_ will be substituted by the calculated spam score for the message _REQD_ will be replaced by the threshold value see above This setting allows US ASCII non control characters only character codes 32 127 Do NOT use the character Note The SpamAssassin Filter is the only filter that supports substitutions in the subject tag e g spam score 4 9 2 3 Tweaking The SpamAssassin Rule Set If you want to further customize SpamAssassin consult the SpamAssassin docu mentation files included with the installation files find it in the sa doc subdirec tory of the installation directory To customize the SpamAssassin rule set for example to modify the score for a particular rule you can do so by editing the corresponding configuration file using your favorite text editor See the document Mail_SpamAssassin_Conf htm for details
4. Sets the directory where the mail files will be stored If empty the system tempo rary directory is used Note 1 Make sure that CleanMail or the account used by the service normally the system account has access permissions to create read write or delete files in the target directory This is especially important if the target directory resides on a network drive Note 2 Make sure that unprivileged users do not have access to this directory otherwise a user s mail would be readable by others Note 3 If you have a virus scanner with On Access scanning enabled it may interfere with the mail storage whenever a virus message is stored As a result you may see error messages in CleanMail s log file 4 10 2 Max No of Days This sets the maximum number of days messages are kept in storage Leave this setting empty if you don t want to use this feature 4 10 3 No of Messages This sets the number of messages to store in the cache Once the limit is exceeded the storage manager starts deleting old messages Leave this setting empty if you don t want to use this feature 4 10 4 Max Cache Size This sets the maximum disk space used by the cache Once the limit is exceeded the storage manager starts deleting old messages Leave this setting empty if you don t want to use this feature 33 Chapter 5 Monitoring The status display of CleanMail lets you monitor CleanMail s activities There are a traffi
5. Note 1 Configuration changes in files other than 1ocal cf are not backed up upon installation of an update If you want to keep your changes copy the files you changed and restore them after installation Note 2 To validate your changes use the lint option of SpamAssassin cd InstallationDirectory sa spamassassin x siteconfigpath salruleset lint 4 9 3 CleanMail SpamAssasssin Options 4 9 3 1 Spam Mail Policy Options On the first page of the spam mail policy options you can choose what happens with spam See Filter Result section4 2 2 for a list of different spam mail policies The second page allows to set a Reject and Delete threshold Mails are deleted reject delete policy if the spam score is higher than this value regardless of the policy setting you entered on the previous page 31 CleanMail SpamAssassin Filter Wizard EX Spam Mail Policy Options Choose what to do with spam mails Define what to do with spam mails If you choose to reject mail the sending mail transfer agent MTA notifies the sender that his mail could not be delivered If you choose to accept mail the sender will assume that his mail was delivered without problems accept deliver junk relectideliver accept delete reject delete accept redirect reject redirect next gt cons Figure 4 6 Spam Filter Policy Setup 4 9 3 2 Multiple SpamAssassin Filters If you are using multiple SpamAssassi
6. Home on one 1 computer to be used by multiple users It is expressly forbidden to install CleanMail Home for use on multiple computers without paying additional license fees Licensee warrants that they will make a reasonable effort to remove unused licenses of CleanMail Home Please contact us via email at support byteplant com for site licenses and volume discounts DISCLAIMER OF WARRANTY CLEANMAIL AND THE ACCOMPANYING FILES ARE SOLD AS IS BYTEPLANT MAKES AND CUSTOMER RE CEIVES FROM BYTEPLANT NO EXPRESS OR IMPLIED WARRANTIES OF ANY KIND WITH RESPECT TO THE SOFTWARE PRODUCT DOCU MENTATION MAINTENANCE SERVICES THIRD PARTY SOFTWARE OR OTHER SERVICES BYTEPLANT SPECIFICALLY DISCLAIMS AND EX CLUDES ANY AND ALL IMPLIED WARRANTIES OF MERCHANTABIL ITY FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT DUE TO THE VARIETY OF USER EXPERTISE HARDWARE AND SOFT WARE ENVIRONMENTS INTO WHICH CLEANMAIL MAY BE SUB JECTED THERE IS NO WARRANTY FOR TECHNICALLY ACCURATE PER FORMANCE THE USER ASSUMES ALL RISK OF USING CLEANMAIL THE MAXIMUM LIABILITY OF BYTEPLANT WILL BE LIMITED EXCLU SIVELY TO THE PURCHASE PRICE LIMITATION OF LIABILITY NO LIABILITY FOR CONSEQUENTIAL DAM AGES To the maximum extent permitted by applicable law in no event shall 55 byteplant GmbH or its suppliers be liable for any damages vvhatsoever includ ing without limitation damages for loss of business profit business interruption loss of business inform
7. Policy Options 4 9 3 2 Multiple SpamAssassin Filters 4 10 Mail Storage Setup 4 10 1 Storage Directory 4 10 2 Max No of Days 4 10 3 Max No of Messages 4 10 4 Max Cache Size Monitoring Sl Status ee 3 2 LOL bata ae oe eS 5 3 Report 5 4 Statistics 5 4 1 Statistics Graph 5 4 2 Statistics File Maintenance 6 1 SpamAssassin Maintenance 6 1 1 Training The Bayes Database 6 1 1 1 Learning Messages From Storage 6 1 1 2 Using sa learn in a command window 6 1 2 Database Expiry 6 2 Anti Virus Filter Maintenance 7 Reference 7 1 CleanMail Configuration File 7 1 1 General Structure 72 2 Value Types iio R a te ssa a ee 7 1 3 Session Manager Settings 7 1 4 Port Settings 7 1 4 1 General Proxy Port Settings 7 1 4 2 Monitoring Port Settings 7 1 4 3 POP3 Port Settings 7 1 5 Filter Settings 7 1 5 1 General Filter Settings 7 1 5 2 Attachment Filter Settings 7 1 5 3 Blacklist and Whitelist Filter Settings 7 1 5 4 RBL Filter Settings 7 1 5 5 External Filter Settings 7 1 5 6 Return Code Settings 7 1 5 7 Mail Storage Setti
8. Send yourself a test mail Use your account to send a message to yourself or use an e mail echo server e g echo tu berlin de If you want to uninstall CleanMail later remember that CleanMail s uninstall pro gram will not reset the POP3 port of your mail client back to 110 you have to do this by hand 2 2 CleanMail Setup CleanMail setup features a standard Microsoft Windows setup interface and you need only complete a fevv steps You can cancel setup at any time by clicking the Cancel button Double click cleanmail exe or similar filename file on either the distribution media or from the downloaded ZTP file This will launch the CleanMail Setup VVizard Click Next on the Welcome screen Read the CleanMail license and click I accept to agree with this license Choose a folder where CleanMail should be installed The setup program will suggest a default location If you do not want to use the default location you can browse for a specific directory in the provided input field placing CleanMail in a location other than the default will not affect the operation of the program Unless your CleanMail directory already exists either the suggested default directory or one of your choosing the setup program will ask you if it can create that directory Click Yes If you want to change the location of the program click No This will keep you on the directory screen to choose another location The next step
9. Use this filter to store verbatim copies of incoming messages some vvhere on your hard disk or on netvvork attached storage in a folder you can configure External Commandline Filter This is the svviss army knife of mail filtering You can supply your own home made filters and integrate them easily into the filtering pipeline of CleanMail 1 1 POP3 Filtering If you use POP3 filtering CleanMail acts as a transparent proxy for your Internet service provider s POP3 server The connection is initiated by your mail client connecting to CleanMail and CleanMail forvvards this connection request All messages have already been accepted and acknowledged by your ISP s mail server so CleanMail is unable to reject the messages received For this reason there can be no feedback to the sender of a message if a message is classifed as spam and deleted CleanMail is designed to vvork vvith all knovvn POP3 servers and vvith all mail clients supporting the POP3 protocol This includes popular mail clients as MS Outlook Mozilla Thunderbird Eudora or The Batl Note that the APOP and IMAP protocols are not supported Mail retrieved using these protocols is not filtered by CleanMail 1 2 SMTP Filtering The best place to stop SPAM is at the mail server for two reasons e Spam mails can be deleted outright before they enter your system This saves your money as you need less storage bandwidth and less of your users time e If a legit
10. and the editor supplied with Windows notepad may be unsuitable for editing these files Install some other text editor package available in the Internet such as crimson textpad or ultraedit just to name a few 7 1 1 General Structure The configuration file format is similar to the Windows ini file format e The first line identifies the file format version At present only file format versions 3 0 2 1 and legacy files CleanMail version 1 x are supported e Configuration settings are grouped in sections Each section starts with a section label in square brackets 11 e A section may include other sections subsections The section label of such a section repeats the section label of the enclosing section and its own label 42 e Configuration settings are given as lt name gt lt value gt Note that values should alvvays be quoted using double quote characters Empty values denoted by a pair of double quotes vvith no other characters betvveen may be allovvable for some settings e Lines starting with the character are ignored and can be used to add com ments All settings not explicitly overridden in the configuration file take on their default value 7 1 2 Value Types Configuration settings can have the following types boolean Set to either 0 meaning false no disable or to 1 meaning true yes enable In some cases it may be allowable that a boolean value may be empty or unset meaning u
11. attachment You can use the wildcard characters any character and x any number of any character to define attachment types Multiple attachment types can be separated by blanks If 46 empty no messages are deleted The block list is the last attachment type list checked Defaults to a list of attachment types commonly used in virus messages DropListPolicy string Filter action applied to messages containing attach ment s of a blocked type Defaults to reject delete Allowable values are in order of precedence reject redirect accept redirect reject delete accept delete ErrorLineBreak boolean If this is set to true bad line breaks are treated like other MIME errors and handled as defined in the ErrorPolicy setting De faults to false ErrorPolicy string Filter action applied to messages with unrecoverable MIME syntax violations This usually involves malformed attachment specifica tions or other techniques that could be exploited to bypass the attachment filter or virus checkers Defaults to accept deliver Allowable values are in order of precedence accept deliver reject redirect accept redirect reject delete accept delete PassList string Sets the attachment types you want to always accept You can use the wildcard characters any character and x any number of any char acter to define attachment types Multiple attachment types can be separated by blanks The pass list is the fi
12. choose a different setting if desired The policy you apply has to be chosen with the MIME Error Policy setting The Line Break Policy setting controls the handling of wrong line breaks Mes sages with wrong line breaks are passed by default 4 4 Blacklist Filter Setup The Blacklist filter uses static address patterns to check the sender address fields of a message A blacklist filter is very time consuming to maintain and usually not very effective as spammers can easily fake a different sender address 4 4 1 Sender Address Patterns This is the list of sender addresses or address patterns to blacklist You can use the wildcard characters any character and any number of any character for example like in obnoxious site 22 4 4 2 Policy The policy you choose in this setting is applied when a sender matches one of the sender address patterns 4 5 Whitelist Filter Setup The Whitelist filter uses static address patterns to check the sender address fields of a message Mail from whitelisted addresses is accepted and bypasses all filters but the attachment filter and anti virus filter You can configure those filters to pass whitelisted messages as well 4 5 1 Sender Address Patterns This is the list of sender addresses or address patterns to whitelist You can use the wildcard characters any character and any number of any character for example like in tbyteplant com Important For
13. figuration page 4 1 1 POP3 Server and Port Settings This page allows to set the basic connectivity settings of the proxy port you are configuring Incoming IP Address Port 17 Choose one of the IP addresses available Use lt all interfaces gt if you want the proxy to listen on all interfaces This setting will make CleanMail listen on all IP addresses including the loopback interface 127 0 0 1 Usually the port number will be the POP3 port number 110 Outgoing IP Address Port The outgoing IP address cannot be configured in advance It depends on the ac count a user wants to connect to and it is specified in the mail client see below The outgoing port number is always set to 110 4 1 2 Changing the Mail Account Settings If you want to use the POP3 proxy to filter incoming mail you have to change the mail account settings in the configuration of the mail client software you use Usually you will find the following settings Outgoing mail server SMTP server Do not modify this setting the POP3 fil ter of CleanMail does not interfere with outgoing mail Incoming mail server POP3 server Write down this setting and modify it to the hostname or to the IP address of your CleanMail server Make sure you use the POP3 protocol to fetch mail User Account Modify this setting to username mailserver using the mail server name you wrote down in the previous step Password Leave this unchanged Note that C
14. is to decide upon the name of the CleanMail program group name that you will see in the Start Menu CleanMail suggests a default but you can 10 change that to whatever name you would like changing the name of the CleanMail program group will not affect the program operation in any way After you have decided upon a name click Next There are some optional CleanMail Setup tasks that you may choose to have done You can select these tasks by clicking on the appropriate check box e Install additional ruleset Installs additional spam filtering rules not part of the SpamAssassin distribution Create a desktop icon put a shortcut for CleanMail Administration Wizard on your desktop e Create a quick launch icon put a CleanMail Administration Wizard icon into the quick launch bar e Windows Firewall Setup check this to create Windows Firewall exceptions that allow mail transfers to pass through CleanMail not for all versions of Windows 8 Setup CleanMail Server ojo ea Select Additional Tasks Which additional tasks should be performed Select the additional tasks you would like Setup to perform while installing Clean Mail ver then click Next Optimize spam filtering results install additional nulesetsi Additional icons Create a desktop icon for CleanMail Admin v Create a Quick Launch icon for CleanMail Admin Windows Firewall Setup 7 Allow connections to Clean Mail s SMTP POP3 ports recommended
15. make sure you enter the license key correctly use copy paste CTRL C and CTRL V keys To obtain a license key please visit our 2 5 Uninstalling CleanMail When uninstalling CleanMail do not forget to undo any changes you might have made in your firewall configuration or mail client configuration CleanMail itself can be uninstalled in one of two ways 13 2 5 1 Using CleanMail Uninstall This program is located in the CleanMail program group the program group name may be different if you chose another name during setup You can access it through the Start menu Find and select Uninstall CleanMail to run the uninstall program You will be asked if you want to completely remove CleanMail and all of its com ponents Click Yes to continue with the de installation or No to cancel If you click Yes all installed files will be removed any configuration files you created will be preserved If removal was successful a success message will appear if you encounter problems during de installation please visit the Trouble Shooting section of this manual Click okay to close this message CleanMail is no longer installed on your computer 2 5 2 Using The Microsoft Windows Control Panel Select Add or Remove Programs icon and then CleanMail This will launch the CleanMail uninstall program Follow the process as described in the previous section section2 5 1 14 Chapter 3 Concepts This chapter is
16. of external filter setup Here you can control which program to run with what arguments 24 CleanMail SpamAssassin Filter Wizard es Command Line and Exit Codes Set the command line and the exit code policies for this filter The command line setting specifies the filter executable and optional command line arguments You can use IN OUT and ERR as placeholders for input output and error files When the filter is executed these placeholders will be replaced with the real file names sa spamassassin exe FLAGS x siteconfigpath CONFIGPATH e 255 kel Some filters do not modify a message or have no meaningful output other than the exit code If you unset this option the filter output is discarded and the filter input used instead 4 Use filter output Specify what to do depending on the exit code of the filter Use the test buttons to see if your filter works Exit Code Policy 0 accept deliver 255 reject deliver Test with Sample Test with Sample Virus lt Back next gt L g nci Figure 4 2 External Filter Setup 4 7 1 1 Message Text Input and Output The message to check is passed to the standard input of a external program If a program does not modify a message virus checkers for example only analyze a message you can choose to ignore the output of a program in this case the unmodified message will be forwarded to the next filter Otherwise standard output of
17. or from the command prompt Try to connect with telnet to both your ISP s POP3 server and to CleanMail Once you have seen the POP3 server s welcome message starting with OK issue a QUIT command Here is the transcript of a sample telnet session 12 C gt telnet localhost 110 Trying 127 0 0 1 Connected to testl Escape character is OK CleanMail POP3 proxy ready QUIT OK closing connection Connection closed by foreign host If everything works you will get exactly the same replies both times If you can t connect to the ISP s POP3 server troubleshoot your firewall configuration or it might be the POP3 server or the connection to the Internet is down If you can t connect to CleanMail look into CleanMail s log file for an error message 2 3 3 Firewall Configuration Once you have installed CleanMail Home it will be CleanMail that connects out to your Internet service provider s POP3 server and no longer your mail client For CleanMail to work properly you need to allow this connection in your fire wall configuration To find out how to do this consult the documentation of your firewall software If CleanMail is unable to connect to the POP3 server you will find unable to connect to outgoing server messages in cleanmail log 2 4 Registering CleanMail To register CleanMail enter the registration name and license key you received when you purchased in the registration window To
18. security reasons anti virus filters and the attachment blocker by default ignore whitelisting You can change this behaviour by removing the check mark from the Ignore Whitelist setting in these filters 4 6 RBL Filter Setup DNS blacklists are Internet resources maintaining databases of known spam relay hosts Mail servers can query these databases in an efficient manner using the DNS domain name service protocol The RBL filter rejects all mail that has been relayed by a blacklisted host The RBL filter is highly efficient and typically capable of getting rid of half the spam messages at a low resource usage 4 6 1 DNSBL Zone List This setting defines the DNSBL blacklists to query If a relay host is listed in one of these zones the message is blocked using the filter policy you can define below Choose with care because picking the right zones affects the RBL filter s effec tiveness When in doubt stick with the default setting 23 4 6 2 Policy If a relay host is listed on one of the configured DNS blacklists the mail is blocked using this policy 4 6 3 Relay Check Option All relays forwarding a mail message prepend a new received header field to the mail header with information about the servers involved host name and IP the protocols used and a time stamp The header lines are parsed by the RBL filter to find the IP addresses to check against the DNS blacklists defined in the Zone List setting The last rece
19. that mailed to accounts in your domain in the last 24 hours or yesterday complete with message counts and sizes Top Hosts A list of mail hosts IP address and name that delivered mail in the last 24 hours or yesterday complete with message counts and sizes Top Spam Hosts A list of mail hosts IP address and name that delivered a spam message in the last 24 hours or yesterday complete with message counts and sizes For all reports you can change the sort order by clicking the column headers After selecting a line in a report you can right click the line or press the Message button to choose from a menu of actions Open Message The message is opened using the application associated with eml With many versions of Windows the default application associated Microsoft Excel is a registered trademark of Microsoft Corporation 35 with this file type is Outlook Express This feature requires that a copy of the message is cached in a mail storage This action maybe unsafe to use with virus messages depending on the associated application Send Message A verbatim copy of the message is submitted to a recipient of your choice using a mail server of your choice You can use this to forward a blocked message to its original recipients This feature requires that a copy of the message is cached in a mail storage This action maybe unsafe to use with virus messages depending on the mail client used by the recipient View Messag
20. to use double quotes if a path or file name contains blanks CAUTION Never learn forwarded spam mails The act of forwarding modi fies mails in unexpected ways to learn a forwarded mail will be useless or even counter productive Learn single messages Find the X CleanMail MessageID header in the message you want to learn Using the MessagelD you can locate the em1 file in the mail storage directory To learn a message as spam from the command window use the following command line cd InstallationDirectory sa sa learn siteconfigpath sa ruleset spam Path To forget or learn as ham use forget or ham instead of the spam op tion Learn a message folder Most mail clients are using the mbox mail folder format or have an export function to export a mail folder to an mbox file Collect the spam messages you vvant to learn in a mail folder and export this folder to an mbox file Then use the follovving commands in a command line window 39 cd InstallationDirectory sa sa learn siteconfigpath sa ruleset spam mbox Path For repeated use create a batch file with the commands above An example is provided in the installation directory of CleanMail If you are using Microsoft Outlook or Outlook Express you can t learn entire mail folders because there is no simple way to export to an mbox file There is not even a way to export a single message to a text file in RFC 822 format T
21. 0 7 1 4 2 Monitoring Port Settings Monitoring ports HTTP ports only support the general port settings and the fol lowing additional settings Allow string A list of IP addresses or hostnames that may access the monitoring port All addresses within private network IP address blocks RFC 1918 are automatically allowed If you want client access over the Internet enter the remote hosts that may access the server Note that dynamic DNS is supported Defaults to an empty value Deny string A list of IP addresses or hostnames that may not access the moni toring port Defaults to an empty value 7 1 4 3 POP3 Port Settings POP3 ports support the general port settings Also POP3 ports may contain mul tiple filter sections describing the filters configured for this port see filter settings sec on7 1 5 45 7 1 5 Filter Settings 7 1 5 1 General Filter Settings ID string Unique short filter identifier used internally A unique ID is automati cally generated by default Allovvable identifiers are not empty and have up to 7 characters IgnoreWhitelist boolean If true the filter is always applied even to whitelisted messages Defaults to false for most filters with the exception of attach ment filters and anti virus filters Name string Filter name used in statistics and log files Filter names should be unique A unique name is usually generated by default Allowable identifiers are not empty and up to 30 c
22. Gs Caz Figure 2 2 Installation Options Click on the Next button to continue CleanMail will now install the program files and options If there were no problems during installation you will see the Finish screen From here you can launch the CleanMail Administration Application If you don t want to launch CleanMail un check the corresponding checkbox Alter natively you can just start the CleanMail service Click the Finish button when done 2 3 Troubleshooting the CleanMail Installation This section is intended to help you if you run into trouble during installation If this section does not help with your problem please consult the FAQ list This page also offers access to some How to documents 11 2 3 1 About Sockets Ports and Listeners A network server is constantly ready to receive incoming connections from net work clients In other words it is listening An SMTP server will be listening on the SMTP port of your machine waiting for incoming connections from other mail transfer agents MTAs mail clients or other mail servers to send mail SMTP simple mail transfer protocol is used to forward or deliver mail and cannot be used to fetch mail POP3 servers listen on the POP3 port providing a service for mail clients only Mail clients can use POP3 post office protocol version 3 to lookup if there are new mails available and to fetch mails POP3 cannot be used to send mail Po
23. Report ul Statistics 22 Configuration A Maintenance SMTP Proxy lt all interfaces gt 25 gt 192 168 0 35 25 Add Filter Whitelist 152 pass messages from whitetsted sender without tering D Attachment Filter Removes dangerous attachments Sis ll L DNSBL Filter ES Remove messages relayed by blacklisted host 22 Delay Filter 7 Delays message acknowledgement bi SpamAssassin Detects and tags spam messages POP3 Connector pop3 isp com 110 gt 192 168 0 35 25 dd Ete Whitelist pass messages from weitetated sender without tering Xs ISS 55 PASS LSS La Attachment Filter 2 5 Figure 3 1 Example Filter Pipeline For this reason the following guidelines should be applied when determining the order of filters in the pipeline e Filters with the lowest resource usage and the highest selectiveness should go first For this reason the attachment filter should always be one of the first filters in the filter pipeline e Filters which use a lot of processing power and with low selectiveness should go last Most people won t delete spam mails without at least giving hu mans the chance to look them over For this reason the selectiveness of the SpamAssassin filter is low while it uses a lot of resources Therefore the SpamAssassin filter should be one of the last filters When configuring CleanMail with the Admin application every new filter will be automaticall
24. ample net gt E Subject SPAM 1003 4 Test spam mail GTUBE To Recipient lt recipient example net gt Date Wed 15 Sep 2004 15 31 22 0200 Content Type text plain charset us ascii Message Id lt GTUBEMessage Gbyteplant internal Content Transfer Encoding 7bit X Spam Flag YES Message ID lt GTUBEMessage Gbyteplant internal x X Spam Checker Version SpamAssassin 3 2 4 200 MIME Version 1 0 X Spam Level X Spam Status Yes score 1003 4 required 4 8 b This is the GTUBE the SPF_HELO_NEUTRAL autolearn no versi Generic MIME Version 1 0 Test for Content Type multipart mixed boundary Unsolicited 4 m lt m Log Output Dec 06 2008 14 08 19 Session 0 SpamAssassin Executing sa spamassassin exe x siteconfigpath sa Dec 06 2008 14 08 30 Session 0 SpamAssassin Command line exit code is 255 Dec 06 2008 14 08 30 Session 0 SpamAssassin Filter result is reject deliver Dec 06 2008 14 08 30 Session 0 SpamAssassin Spam score 1003 4 m Filter finished Figure 4 3 Test Filter Screen interpreter with your batch file as an argument Here is an example what this might look like for VVindovvs XP cmd Q D C c dir batch bat IN OUT SERR To learn more about cmd type help cmd in a command prompt window 4 7 2 Advanced Settings The advanced settings allovv choosing a timeout for the external program a size lim
25. ation or any other pecuniary loss arising out of the use of or inability to use this software product even if byteplant GmbH has been advised of the possibility of such damages LEGAL NOTICES CleanMail Home uses the spam filtering engine of the open source project SpamAssassinTM SpamAssassin and Powered by SpamAssas sin are trademarks of the Apache Software Foundation The SpamAssassinTM open source project resides at http spamassassin apache org CleanMail uses the cairo http www cairographics org and wx Widgets http www wxwidgets org libraries 56
26. be contacted by email to support byteplant com Chapter 2 Installation The installation section covers system requirements CleanMail installation and CleanMail uninstallation procedures CleanMail installs itself as an autostart program located in the auto start subdirec tory of the start menu CleanMail is usually minimized displaying a small icon in the system tray usually in the lower right corner of the desktop By right clicking this icon you can pop up a menu to maximize CleanMail CleanMail runs as a Windows Service Thus Windows 2000 XP 2003 Vista 2008 is required Note Depending on its configuration Windows XP sometimes hides this icon To make the CleanMail icon reappear click on the arrow symbol left of the system tray 2 1 Quick Start Installation Procedure This document explains how to configure CleanMail Home for use with a POP3 email client like e Microsoft Outlook Outlook Express Eudora e Pegasus The Bat e and many others more 2 1 1 CleanMail Installation When you start CleanMail for the first time the quick start wizard will guide you through the installation process Download CleanMail Install CleanMail using the setup program Launch the CleanMail Admin application The Quick Start Wizard will appear On the POP3 settings page follow the instructions to configure your mail client Step to the following pages and make adjustments according to your wishes Save the con
27. c display a log display mail reporting and statistics views You can also monitor your CleanMail installation using a vveb brovvser Use this URL to access the monitoring page served by the CleanMail service while it is running http ocalhost 8086 index html 5 1 Status This page shows CleanMail s status including license and version information and a traffic chart 5 2 Log This page is a live view of messages written to CleanMail s log file cleanmail log located in the installation directory The verbosity of the messages in this file can be modified using in the configuration wizard section 4 1 To view the logfile with your default text editor press the View Log File With Editor button To get a deeper understanding of POP3 and what happens in the log especially when you enabled detailed logging please refer to RFC 1939 5 3 Report For every mail received or rejected a line is added in CleanMail s mail log file CleanMail mail csv The mail log file is a list of comma separated val 34 CleanMail Admin oJ a File View Proxy Setup Filter Setup Help Status Lj Log Report LLJ Statistics Configuration A Maintenance Jul 03 2009 16 39 57 Session 0 DATA Jul 03 2009 16 39 57 Session 0 554 No valid recipients Jul 03 2009 16 39 58 Session 0 RSET Jul 03 2009 16 39 58 Session 0 250 Reset OK Jul 03 2009 16 39 58 Session 0 MAIL FROM lt shu_chiew zdnetasia c
28. e The contents of the message are displayed in an internal viewer window The display is plain ASCII text no attachments are unpacked and no HTML code is interpreted so it is safe to use this action with virus mes sages This feature requires that a copy of the message is cached in a mail storage View Envelope Displays mail transmission data depending on the transmission protocol used This feature requires that a copy of the message is cached in a mail storage Transmission Log Searches the CleanMail log file to find the session that actu ally handled the selected message and displays all information about this session The transmission log may be unavailable if the log file has already been cycled To get the most from this feature enable detailed logging Copy To Clipboard Use this menu item to copy ie the message subject sender or the recipient to the clipboard Learn Use this menu item to train the SpamAssassin Bayes database section6 1 1 or to blacklist or whitelist a sender address If you use black list or whitelist filters be sure to check and optimize these filters regularly Bloated blacklists whitelists may degrade overall performance Bayes train ing requires that a copy of the message is cached in a mail storage blacklist ing or whitelisting works even when the message is not stored 5 4 Statistics CleanMail maintains a number of counters to collect statistics data such as raw SMTP network traffic mail count
29. ed accept delete The filter found unwanted content Receipt of the mail is acknowl edged but the mail is deleted The mail simply vanishes the sender is not notified and the recipient never sees it accept deliver whitelisted The sender address is whitelisted All filters except attachment blockers and anti virus filters are bypassed and the mail is ac cepted and delivered accept deliver license count exceeded The filter was disabled because the re cipient address count covered by your license was exceeded The mail is accepted and delivered All messages that have been processed by CleanMail will have a X CleanMail Result header field This can be used by the mail client or server to quarantine or delete mails See your mail software s documentation to find out how to set up filtering rules Note Filter results lower down in the list take precedence Filters further down in the filter pipeline can override results of earlier filters For a discussion of this see Filter Pipeline section 3 2 4 2 3 Subject Tag Set the text added to the subject of mails considered spam This setting allows US ASCII non control characters only character codes 32 127 4 3 Attachment Filter Setup Most worms and viruses are spread by attachments Getting rid of messages con taining potentially malicious attachments before even starting virus checkers or spam filters can be very helpful to reduce system load 20 4 3 1 At
30. ers and filter result counters 5 4 1 Statistics Graph The statistics page of the admin application offers a graphical visualization of some core counters total mail received mail passed mail blocked Historical data dis 36 CleanMail Admin coe ots a File View Proxy Setup Filter Setup Help Status Ljlog Report hil Statistics 2 Configuration A Maintenance Display Type Message Count v Time Range lt auto gt y Refresh Port SMTP Proxy y 2006 2007 2008 2009 8000 8000 IN 06 6 Passed E 93 4 Blocked 6000 7 yy 00 0 Not Filtered 6000 Figure 5 2 Statistics Vievv played is read from the statistics file section5 4 2 Additionally the graph is continuously updated vvith live data 5 4 2 Statistics File The statistics data is kept in a file called CleanMail Statistics csv lo cated in the installation directory The statistics file is a list of comma separated values and thus can be easily read and processed by spread sheet softvvare such as Microsoft Excel The data is organized in lines each line the counter values for a day The first field of a line contains the date The statistics file is cycled every day at midnight or whenever the service is stopped At the same time today s values will be added or updated Once the date of the first line is older than 365 days CleanMail will delete this line This way the statistics file keeps data
31. esides If you find bayes_toks expire files there this indicates expiry failures You may consider disabling automatic expiry as implemented by SpamAssassin add the following line to your local cf file bayes_auto_expire 0 Instead ei ther run database expiry regularly by hand or use the built in Windows scheduler to run expire bat daily located in your installation directory Microsoft Microsoft Outlook and Microsoft Outlook Express are registered trademarks of Microsoft Corporation 40 6 2 Anti Virus Filter Maintenance Please update the virus signature files of your virus checker regularly Read your virus checker s documentation to find out what you have to do to keep the virus signature databases up to date 41 Chapter 7 Reference 7 1 CleanMail Configuration File CleanMail s configuration is saved in a plain text file cleanmail cf For easy configuration you can access the configuration settings using the cleanmail admin application but advanced users can also use a simple text editor to change the settings by modifying the file directly Note To make CleanMail re read its configuration file simply restart the service using either the Windows services manager or the admin application choose Ap ply Settings from the file menu Likewise the admin application only re reads the configuration file upon restart Note Some configuration files originated on other operating systems than Win dows
32. figuration by pressing the Finish button on the last page Now retrieve a couple of mails from your mail box if necessary send your self a couple of test mails If you run into troubles see Troubleshooting the Installation for troubleshooting tips In your mail client add mail filtering rules to automatically move spam mails to a separate mail folder or to automatically delete them Refer to the manual of your mail client for instructions on how to do this Figure 2 1 Mail Path with CleanMail Filtering 2 1 2 Configuring Your Email Client for CleanMail When the quickstart wizard is finished you have to change the mail account set tings in your email client software Go to the mail account settings of your email client Usually you will find the following settings e Outgoing mail server SMTP server Do not modify this setting CleanMail does not interfere with outgoing mail e Incoming mail server POP3 server Write down this setting and modify it to localhost or 127 0 0 1 Make sure you use the POP3 protocol to fetch mail e User Account Modify this setting to username mailserver using the mail server name you wrote down in the previous step Password Leave this unchanged Note that CleanMail does not support the IMAP protocol If your mail client is configured to use IMAP reconfigure it to use POP3 Repeat this procedure for all mail accounts and mail clients you use Test your new settings immediately
33. filter settings common to all filters Please read Filter Pipeline section 3 2 for an intorduction to filter pipelines 4 2 1 Filter Name Filter names are used to identify individual filters in statistics charts and reports The name should be unique If you do not have more than one filter of the same type there is usually no need to override the default name Therefore this setting is usually hidden It is only accessible once you have more than one filter of the same type in use 4 2 2 Filter Results All filter configurations have a setting that allows you to choose what happens with a mail if the filter finds unwanted content such as a virus or spam The following summarizes the filter results you may encounter and their reasons accept deliver The filter did not find unwanted content accept deliver skip size exceeded Some filters do not check mails larger than a configurable size For example spam mails are typically small so the SpamAssassin filter by default passes large mails without checking 19 accept deliver junk The filter found unwanted content but the mail is accepted and delivered nonetheless If the Subject Tag setting is not empty Clean Mail will flag the message as junk by modifying the subject accept deliver unknown result For some reason the filter was unable to check the message The filter will write additional information about the problem to cleanmail log The mail is accepted and deliver
34. for up to one year back Statistics counters are identified by descriptive names The data collected includes the following e Totals counted for a proxy port mails filtered mails passed mails blocked total traffic received sent on the incoming outgoing ports e Filter results for different filters counted separately for each proxy port The number of attachments blocked by the attachment blocker and the num ber of mails were MIME violations were detected only if attachment filter is used 37 Chapter 6 Maintenance CleanMail itself needs no maintenance but the mail filters such as SpamAssassin do 6 1 SpamAssassin Maintenance SpamAssassin requires regular maintenance of its Bayes database Some of this is done automatically but training the Bayes database learning false positives or false negatives is something that should be done regularly by the administrator Otherwise SpamAssassin filtering quality will be less than optimal or may even decline 6 1 1 Training The Bayes Database Some spam messages aren t detected by the static rule set of SpamAssassin false negatives and some are tagged as spam even when they aren t false positives Bayes training in short is about teaching SpamAssassin to do better for similar messages in the future The program to train the database is sa learn which is part of the SpamAssas sin distribution You can start sa learn from the admin application or manually
35. from a command line window Note The results of the Bayes tests are ignored by SpamAssassin until at least 200 messages have been learned 6 1 1 1 Learning Messages From Storage If you configured a mail storage filter you can learn messages directly from mail storage Locate the message in the Journal Report of the admin ap plication Right clicking the message opens a menu that allows learning messages 38 Learn As Ham The message is learned as a ham message Learn As Spam The message is learned as a spam message Forget All database entries already learned from a message are deleted If you accidentally learn a spam message as ham or spam you can undo it this way Depending on how you configured the the mail storage filter a message file may have been deleted already when you try to learn it as either spam or ham To avoid this in the future change your mail storage settings to keep a longer backlog of older messages 6 1 1 2 Using sa learn in a command window Using sa learn directly allows learning multiple messages or entire mail folders at once and it gives you more flexibility to adapt your CleanMail installation to your environment The documentation of sa learn can be found in the sa doc subdirectory or However the official documentation has to be taken with a grain of salt as it hasn t been written with Windows as a target operating system in mind Most important Beware of blanks in pathnames Be sure
36. haracters SubjectTag string If not empty the message subject is modified to indicate that a message is junk This setting allows US ASCII non control characters only character codes 32 127 The default setting is SPAM Note This setting has no effect for the SpamAssassin filter Change the local cf file instead see SpamAssassin documentation 7 1 5 2 Attachment Filter Settings Attachment filter settings are defined in an AttachmentConfig section Filters AttachmentConfig Attachment filters support the following additional configuration options BlockList string Sets the attachment types you want to block deliver the mes sage with the attachment s removed You can use the wildcard characters any character and x any number of any character to define attachment types Multiple attachment types can be separated by blanks If empty no at tachments are blocked The block list is the first attachment type list checked attachments that match a type pattern on this list are not checked against the drop list Defaults to a list of attachment types that may carry macro viruses BlockListPolicy string Filter action applied to messages containing attach ment s of a blocked type Defaults to reject deliver Allowable values are accept deliver reject deliver The attachment is always removed DropList string Sets the attachment types where you want to delete the entire message if it contains a restricted
37. here are some tools around look for out 1ook2mbox or similar with your favorite Internet search engine but your mileage may vary However there is a way even if you are using Microsoft Exchange as mail server This requires the administrator to install one email client other than Outlook or Outlook Express This mail client can then be used to fetch the mails to learn by POP3 or IMAP A step by step example using Mozilla Thunderbird is described on this 6 1 2 Database Expiry As SpamAssassin continues to learn from spam and ham mails its Bayes database continues to grow SpamAssassin regularly checks if the database size exceeds certain limits 150 000 tokens or words about 10MB in database size Once the limit is reached old tokens words that were not encountered in mails for a long time are removed from the database This is called database expiry On slow systems it can happen that database expiry takes longer than the SMTP session timeout In this case the automatic database expire fails and you may need to expire the database manually SpamAssassin database maintenance is best done from the maintenance tab of the admin application This tab shows you some database statistics like the number of words tokens learned and the database file size By pressing the Expire Now button database expiry is started Be prepared that expiry usually takes several minutes to complete Note Check the directory where the database r
38. imate email is identified as spam false positive the sender can be notified that his message might not be read by the recipient SMTP filtering is supported by CleanMail Server only and not available in Clean Mail Home 1 3 Overview Installation procedures and recommended network configurations are covered in Installation chapter 2 This chapter also introduces the CleanMail application This application gives you access to all configuration options and lets you view the CleanMail filtering status and statistics To learn about the concepts implemented in CleanMail see Concepts chapter 3 Configuration of CleanMail is described in Configuration chapter 4 To find out what happens to your mail CleanMail offers a lot of useful monitoring features Learn about these capabilities in Monitoring chapter 5 CleanMail does not require maintenance but some of the filters employed by CleanMail do See Maintenance chapter 6 to find out about regular maintenance required by SpamAssassin and virus filters See the Reference chapter 7 chapter for details about the structure and content of the CleanMail configuration file See Licensing chapter 8 for ordering and license details There are additional resources available online Take a look at the FAQ list if you are running into problems You will also find some How to documents there You may also want to look in the CleanMail support forum CleanMail support can also
39. intended to help you understand the basic concepts in the design of CleanMail Servers 3 1 Proxy Ports A proxy is a server that sits betvveen a client and a server The proxy intercepts all requests to the server to either handle them by itself or to forvvard them to the server VVith POP3 filtering the client is your mail client trying to fetch mail and the server is your ISP s POP3 server The mail client that connects to CleanMail does not see any difference in the ser vice your ISP s POP3 server usually provides 3 2 Filter Pipeline CleanMail feeds incoming mail to a series of mail filters the so called filter pipeline Examples of mail filters are the built in attachment blocker third party virus checkers or SpamAssassin Each filter analyzes the message and returns a filter result telling CleanMail what to do with it Example filter results are accept and deliver or reject and delete The overall filtering result is always the vvorst result for example if the virus checker returns reject and delete it will override another filter returning accept and deliver The location of a filter in the filter pipeline matters To help conserve resources and to increase throughput filters lower down in the filter pipeline are not invoked if an earlier filter has already decided that a mail should be deleted 15 CleanMail Admin fs oe x File View Proxy Setup Filter Setup Help A Status iL Log 2
40. is default is overridden in other filters based on the command line filter UseDOSPathNames boolean Set to true if the filter is a DOS program that re quires DOS 8 3 file names on the commandline This setting has no effect under operating systems other than Windows Commandline filters may contain multiple return code sections 7 1 5 6 Return Code Settings Return codes are defined in ReturnCode sections Filters CommandLineConfig ReturnCodes ReturnCode Code numeric The program exit code Allowable values are in the range of 0 to 255 Policy string Sets the filter action to apply if the command line program returns the exit code defined in the Code setting Allowable values are accept deliver accept deliver junk reject deliver reject redirect accept redirect reject delete accept delete 49 7 1 5 7 Mail Storage Settings Mail storage filter settings are defined in a CacheConfig section CacheDirectory string Specifies the directory where messages are stored De faults to empty If empty the filter will store files in the temporary directory MaxCacheDays numeric Sets the maximum number of days messages are kept in storage Values can be in the range of 1 to 31 days Defaults to unset MaxCacheFiles numeric Sets the number of messages to store in the cache di rectory Once the limit is reached for every new message stored the oldest message is deleted Allowable values depe
41. it and setting the memory usage 4 7 2 1 Timeout If the external program does not return a result vvithin the set timeout period the program is terminated and the filter result is set to accept deliver unknown result section4 2 2 The program will also be terminated when the SMTP session times out or if the MTA that connects to CleanMail disconnects The SMTP timeouts used by most MTAs are in the range of 5 to 10 minutes If you set a timeout a value in the range of 3 4 times the normal execution time is advisable External filter programs should not take longer than 20 seconds to execute 26 4 7 2 2 Ignore Whitelist Use this setting to configure if the filter should run for whitelisted senders or not This setting is disabled by default for all types of external filters with the exception of anti virus filters where it is enabled by default for security reasons 4 7 2 3 Skip Size Spam and virus messages are usually small To conserve system resources and increase throughput it is recommended to skip filtering mails exceeding a certain size 4 7 2 4 Memory Usage Specify here how much system RAM your filtering program needs This setting helps CleanMail to optimize resource allocation Worst case memory usage of virus checkers for large mails is usually about 3 4 times the size of the checked mail 4 7 3 Return Code Policy On this page configure the mapping of exit codes 0 255 to filter results Clam Anti Vi
42. ived header at the top of the message header marks the transfer to the server han dling final delivery and the first received header contains information about when a message was first submitted for transmission to an SMTP server Between these entries there can be any number of relays forwarding the message The first and last received headers can be the same when a message was directly submitted to your server The Relay Check Option defines which received headers relays are checked by the filter If DNS blacklists contain the IP addresses used by dial up services you can reduce the risk of false positives by skipping the DNSBL check for the first received header created when a dial up sender submits his message to the first SMTP server Note that the last received header final delivery will always be checked even when there is only one received header Allowable values are all all but first andlast only The default setting is all but first 4 7 External Filter Setup The external filter is used to pass a mail through another program The SpamAs sassin filter and the anti virus filter both are based on external filters External filters can be used for many tasks such as archiving mails providing additional statistics or storing mails in an SQL database The CleanMail development team is ready to provide custom made filters designed to fit your specifications 4 7 1 Command Line The command line setting page is the core
43. ived header created when a dial up sender submits his message to the first SMTP server Note that the last received header last relay will always be checked even when there is only one received header Allowable val ues are all all but first and last only The default setting is all but first Timeout numeric When the timeout is exceeded all DNS queries are cancelled and the message is forwarded to the next filter Result unknown Recom mended values are in the range of 15 30 seconds the default is 30 seconds 7 1 5 5 External Filter Settings These settings can be used with all filters based on this filter type External filters may also be used by themselves in this case the settings are defined in a Comman dLineConfig section Filters CommandLineConfig External filters support the following additional configuration options CommandLine string Sets the command line to execute this filter You can use SINS S0UTS or SERRS as placeholders for the input output and error file names If INS is not used the input message is available as standard input if SOUTS is not used output is collected from standard output if SERRS is not used error output is collected from standard error The defaults depend on the filter implementation CommandLineOutput boolean Some filters do not modify a message If you unset this option the filter input is forwarded to the next filter in queue and any filter output other tha
44. iver junk reject deliver reject redirect accept redirect reject delete accept delete 7 2 POP3 command quick reference POP3 is readable by humans This section provides the necessary knowledge to interpret the information given in cleanmail s logs if you enable detailed logging and understand what happens during a POP3 mail retrieval session The complete specification of the POP3 protocol is given in the RFC 1939 document and avail able online http www 1etf org rfc rfc1939 txt 51 255 7 2 1 Example POP3 Session For testing purposes you can also retrieve mail by means of a text only terminal session e g using telnet to connect to the POP3 port of a POP3 server Once the connection has been opened the POP3 server issues a one line greeting Here s an example OK pop3 byteplant com ready Now is the time for the client to sign in issuing the USER and PASS commands USER test OK PASS fred OK The LIST command can now be used to get a listing of all messages stored in the mail box LIST OK 2 messages 344 2 857 In the example two messages are in the mailbox numbered 1 and 2 with lengths of 344 and 857 byte The RETR command now fetches the message the argument is the number of the message to be fetched RETR 1 OK 344 octets Received from 127 0 0 1 From god heaven To mortal earth Subject Test Message This is the body of the test me
45. leanMail does not support the IMAP protocol If your mail client is configured to use IMAP reconfigure it to use POP3 Repeat this procedure for all mail accounts and mail clients you use Test your new settings immediately Send yourself a test mail Use your account to send a message to yourself or use an e mail echo server e g echo tu berlin de 4 1 3 Logging Options The log output can be seen on the Log page of CleanMail Admin or by viewing the file cleanmail log The log file is cycled whenever its size exceeds the limit or at midnight when a configurable number of days has passed The verbosity of the log file is controlled by the following flags 18 e Extended logging adds some more output to the log that might be interesting Turning this option on will log the To From and Subject mail headers of every mail received Detailed logging among other things adds a transcript of the entire POP3 communication to the log This is most useful for debugging mail transport problems Filter error logging collects error or debug output of the mail filters and writes it to the log file Virus filters often log the type of virus found to their error output With this option on you can see it in CleanMail s log The Hide Receive Mail Status setting disables the small popup window that appears in the lower right corner of the desktop displaying the mail download progress 4 2 Mail Filter Setup This section discusses
46. n 7 1 4 1 General Proxy Port Settings These settings apply to all types of ports 44 IncomingConnectionCount numeric Sets the length of the listening queue on the proxy port server socket Defaults to 20 allowable values are operating system dependent IncomingPort numeric Sets the port number of the server socket The default depends on the protocol involved Allowable values are in the range of 0 to 65535 IncomingServer string Sets the IP address or name of the server socket If empty the socket is bound to all interfaces Defaults to an empty value IncomingTimeout numeric Sets a timeout in seconds for waiting on data from the client connected Upon timeout the incoming connection is reset and resources held by the connection are freed The default depends on the pro tocol involved Allowable values are in the range of 10 to 3600 Name string Port name used for housekeeping purposes Port names should be unique The default depends on the protocol involved OutgoingConnectionCount numeric Set the maximum number of simultaneous active connections on this port Defaults to 1000 allowable values are in the range of 1 to 1000 OutgoingTimeout numeric Sets a timeout in seconds for waiting on data from the server connected Upon timeout the incoming connection is reset and resources held by the connection are freed The default depends on the pro tocol involved Allowable values are in the range of 10 to 360
47. n filters by default all filters use the same SpamAssassin configuration settings stored in the local cf file of your default rule set directory the sa ruleset subdirectory of your installation If you intend to use different SpamAssassin configurations for your SpamAssassin filters copy the sa ruleset directory to a different directory and update the fil ter settings of the SpamAssassin filter that uses this directory accordingly a special setup page to enter the directory becomers visible in the SpamAssassin filter setup wizard as soon as you add a second SpamAssassin filter to your configuration Note that CleanMail s installer only updates the default SpamAssassin rule set never any additional rule sets You may need to update additional rule set directo ries add remove update configuration files other than 1oca1 cf manually 4 10 Mail Storage Setup The mail storage filter can be used to archive mails on the file system of your server The mail files x em1 are stored in MIME Format RFC 822 and can be viewed with the majority of mail client software In addition to the mail file message transmission data such as the SMTP sender and recipients is saved in an envelope file The envelope file can be viewed with a text editor Many of the message browsing and learning functions see raining The Bayes Database section6 1 1 require that a message has been saved with a mail storage filter 32 4 10 1 Storage Directory
48. n the exit code is ignored Defaults to true in plain command line filters but this default is overridden in other filters based on the command line filter 48 CommandLinePriority numeric Sets the scheduling priority of the process exe cuted On Linux Mac this setting corresponds to the process nice value and defaults to 0 normal priority On Windows allowable values are 0 for low priority and 1 for normal priority the default CommandLineTimeout numeric Sets a timeout in seconds If the timeout is exceeded the message is accepted without changes Result unknown Al lowable values are in the range of 10 1000s Defaults to 60s in plain com mand line filters but this default is overridden in other filters based on the command line filter MaxFilterSize numeric Spam and virus messages are usually small To con serve system resources and increase throughput it is recommended to skip filtering mails exceeding a certain size given in Byte Allowable values are in the range of 1024 1kB to 1048576000 1000MB Defaults to empty in plain command line filters but this default is overridden in other filters based on the command line filter MaxMemoryRequired numeric Specifies how much system RAM the filtering program needs This setting helps CleanMail to optimize resource alloca tion Allowable values are in the range of 1048576 1MB to 1048576000 1000MB Defaults to empty in plain command line filters but th
49. nd on the file system used De faults to 1000 MaxCacheSize numeric Sets the maximum disk space used in KByte note that values are displayed as MByte in the admin application Allowable values are in the range of 102 400 100MB to to 10 485 760 10GB Defaults to unset 7 1 5 8 Antivirus Filter Settings Anti virus filter settings are defined in a AntiVirusConfig section In addition to the general filter settings and the command line filter settings the anti virus filter supports the following settings CommandLine string In difference to plain command line filters antivirus fil ters substitute the SCANNERS placeholder with the executable defined in the scanner setting The default setting is operating system dependent and vendor dependent Scanner string Specifies the complete path and file name of the command line scanner executable Defaults to empty VendorName string The name of the anti virus scanner vendor Defaults to empty Allowable names are operating system dependent This setting only affects the CleanMail admin application 7 1 5 9 SpamAssassin Filter Settings SpamAssassin filter settings are defined in a SpamAssassinConfig section In addi tion to the general filter settings and the command line filter settings the SpamAs sassin filter supports the following settings 50 CommandLine string In difference to plain command line filters SpamAssassin filters substitute the CONFIGPATH placeholde
50. ngs 7 1 5 8 Antivirus Filter Settings 7 1 5 9 SpamAssassin Filter Settings 7 2 POP3 command quick reference 7 2 1 Example POP3 Session 7 2 2 POP3 commands 1 2 3 a ADA R S Licensing and Contact Information 8 1 Ordering CleanMail 8 2 Support 83 Copyright o es eee eee ek ada R kk RO sala 8 4 License and Usage Terms Chapter 1 Introduction Spam wastes time clogs mail servers can slow your server to a crawl and is very difficult to get rid of Most mailboxes today are constantly flooded with SPAM unwanted advertising of any kind Today the majority of all emails worldwide are spam mails While there is no shortage of solutions to this ever growing problem installing using and working with them often proves to be very complex CleanMail is the mail filter software that was designed from the beginning to make installation configuration and maintenance as simple as possible The CleanMail product family brings the power of the award winning open source spam filter SpamAssassin to the Windows environment The filter pipelining architecture makes CleanMail a flexible multi purpose mail processing tool It allows for an easy integration of additional filtering programs like viru
51. nset undefined unknown numeric Set to a numerical value Numbers must be given as classic decimal numbers a leading denotes negative numbers the dot character is used as decimal point In some cases it may be allowable that a numeric value is unset empty string A sequence of printable US ASCII characters other than the double quote character 7 1 3 Session Manager Settings The first section of the config file is a session manager section labelled WorkstationSessionManager CheckForUpdates boolean Enables or disables the check for program updates at midnight This value defaults to 1 enabled CheckForUpdatesProxy string Sets the HTTP proxy server and port used for the update check Defaults to an empty value in this case CleanMail con nects directly to www byteplant com port 80 to perform the update check DetailedLogging numeric Sets the logging level of cleanmail Individual bits in the binary representation of this number enable different logging options Defaults to 16 1 Detailed logging 43 2 Filter error output 16 Extended logging DNSServer string List of DNS servers to use Defaults to an empty value in this case CleanMail tries to determine the DNS servers automatically MaxBufferSize numeric The maximum message size in Byte larger messages are rejected This is an important security feature if you set this too large users of your mail service can crash your server by submi
52. nstall the virus checker software first If you have not installed the virus checker yet run the anti virus setup wizard again once you have installed the virus checker Note 2 If you want to use F Prot for DOS right click F PROT EXE in the Win dows Explorer to bring up the properties dialog and make sure the close window on terminate or similar property is checked Note 3 If you have a virus scanner with On Access scanning enabled it may interfere with the temporary files CleanMail creates for filtering in the temporary directory To get rid of the error messages that may occur in CleanMail s log file 28 make sure you disable On Access scanning for the temporary directory used by CleanMail On startup CleanMail writes the location of the temporary directory used to the log file cleanmail log Note 4 If you enabled POP3 mail virus checking in your anti virus softvvare don t integrate the virus scanner in the POP3 filter pipeline Othervvise you might end up checking your mails twice Note also that in this case both CleanMail and your virus scanner may contend for the POP3 port of your machine Read Troubleshooting section 2 3 for more information 4 9 SpamAssassin Filter Setup The SpamAssassin filter setup dialog is available in tvvo modes normal and ad vanced Advanced mode is based on the External Filter Setup dialog This section discusses normal mode setup The SpamAssassin filter setup dialog allovvs
53. om gt Jul 03 2009 16 39 58 Session 0 250 OK Jul 03 2009 16 39 58 Session 0 RCPT TO lt e 1j0kdq 00084 00 byteplant com gt Jul 03 2009 16 39 58 Session 0 550 unrouteable address Jul 03 2009 16 39 58 Session 0 DATA Jul 03 2009 16 39 58 Session 0 554 No valid recipients Jul 03 2009 16 39 59 Session 0 RSET Jul 03 2009 16 39 59 Session 0 250 Reset OK Jul 03 2009 16 39 59 Session 0 MAIL FROM lt stamoso domainnews com gt Jul 03 2009 16 39 59 Session 0 250 OK Jul 03 2009 16 39 59 Session 0 RCPT TO lt e1j0kdq 0008tn 00 byteplant com gt Jul 03 2009 16 39 59 Session 0 550 unrouteable address Jul 03 2009 16 39 59 Session 0 DATA Jul 03 2009 16 39 59 Session 0 554 No valid recipients iz Jul 03 2009 16 40 00 Session 0 QUIT L Jul 03 2009 16 40 00 Session 0 221 byteplant com dosing connection Jul 03 2009 16 40 00 Session 0 Connection from 200 42 161 108 dosed 4 m Figure 5 1 Log Vievv ues and thus can be easily read and processed by spread sheet softvvare such as Microsoft A choice of reports based on this data can be viewed on the report tab of the CleanMail admin application Journal All messages handled in the past few days The length of the backlog is limited and depends on mail traffic Top Recipients A list of people that received mail in the last 24 hours or yesterday complete with message counts and sizes Top Senders A list of senders
54. r with the ruleset path defined in the SpamAssassinRulesetPath set ting Also the FLAGS placeholder is substituted with run time flags and should not be omitted The default setting is salspamassassin exe SFLAGS x c SCONFIGPATHS DropThreshold numeric If you set a DropThreshold mails are deleted if the spam score is higher than this value regardless of the return code policy settings Allowable values are in the range of 3 0 to 1000 0 the default is empty If empty this feature is disabled SpamAssassinRulesetPath string Specifies the complete path and of the Spa mAssassin ruleset directory The default is operating system dependent CommandLineOutput boolean Defaults to false see section Command Line Filter Settings section7 1 5 5 for more information CommandLineTimeout numeric Defaults to unset disabled see section Com mand Line Filter Settings section7 1 5 5 for more information MaxFilterSize numeric Defaults to 262144 256kB see section Command Line Filter Settings section7 1 5 5 for more information MaxMemoryRequired numeric Defaults to 268435456 25MB see section Command Line Filter Settings section7 1 5 5 for more information SpamAssassin filters define two return codes one for exit code O non spam or ham message and for exit code 255 spam message As ham message policy accept deliver is recommended and as spam policy one oft the following should be chosen accept del
55. rdering methods Please visit our to find out more 8 2 Support A purchase of CleanMail includes free email support for at least 6 months Please write to us at support byteplant com We will also try to help you with the Trial version of CleanMail if we can Contact us for information regarding other support options by email to sales byteplant com For the latest version always check the CleanMail download page Byteplant offers consulting and the development of custom software Please in quire by email to sales byteplant com 8 3 Copyright CleanMail is copyright Oby Byteplant GmbH 54 Byteplant GmbH Heilsbronner Strasse 4 D 91564 Neuendettelsau Germany E Mail contact byteplant com Company Homepage http www byteplant com 8 4 License and Usage Terms END USER LICENSE AGREEMENT FOR CLEANMAIL This End User Li cense Agreement EULA is a legal agreement between you either an individual or a single entity and byteplant GmbH If you do not agree to the terms of this EULA do not install copy or use CleanMail SOFTWARE PRODUCT LICENSE CleanMail is protected by copyright laws and international copyright treaties as well as other intellectual property laws and treaties CleanMail is licensed not sold LICENSE USAGE TERMS For payment of the license fee the licensee is granted one 1 non exclusive non transferable license to install and use CleanMail Home on one 1 computer at a time or install CleanMail
56. rst attachment type list checked attachments that match a type pattern on this list are not checked against the block list or the drop list Defaults to empty 7 1 5 3 Blacklist and Whitelist Filter Settings Blacklist filter settings are defined in a BlacklistConfig section Filters BlacklistConfig whitelist filters in a Whitelist Config section Filters WhitelistConfig following additional configuration options are supported SenderList string List of sender address patterns You can use the wildcard characters any character and x any number of any character Multiple addresses are separated by blanks Policy string Filter action applied to messages that have a sender address match ing a pattern in the sender list Defaults to reject delete for a blacklist filter and to accept deliver whitelisted for a whitelist filter 47 7 1 5 4 RBL Filter Settings RBL filter settings are defined in a DNSBLConfig section Filters DNSBLConfig The following additional configu ration options are supported ZoneList string List of DNSBL zones to query Multiple zones are separated by blanks Policy string Filter action applied to blocked messages Defaults to reject delete RelayCheck string Defines which received headers relays are checked by the filter If DNS blacklists contain dial up services you can reduce the risk of false positives by skipping the DNSBL check for the first rece
57. rts are identified by port numbers by convention the SMTP listening port is port 25 and the POP3 listening port is 110 As a rule only one program can be listening at the same time at any given port and IP address combination If you run CleanMail and a mail virus checker on the same machine this can be the first trouble you may run into Both the mail virus checker and CleanMail contend for the POP3 port of your machine but only one can use it while the other fails to initialize If CleanMail fails to grab the port it will write an error message in its log file look for a address in use message in cleanmail 1og and pop up a warning dialog To fix this set the POP3 port setting of your mail client to 111 and set the POP3 port number of CleanMail to 111 too the setting can be found on the last page of the configuration wizard This way you will get a checking pipeline like this mail client port 111 CleanMail port 110 antivirus port 110 ISP POP3 server If you want to uninstall CleanMail later remember that CleanMail s uninstall pro gram will not reset the POP3 port of your mail client back to 110 you have to do this by hand 2 3 2 Testing the Basic Proxy Setup POP3 communication was designed to be readable by human eyes Because of this the ubiquitous telnet program proves most useful to test your setup In Windows you can run telnet from the start menu choose Execute and type telnet
58. rus for example returns O if a mail is not infected with a virus 1 if a virus is found Therefore the return code 0 is mapped to the result accept deliver and return code 1 is mapped to reject delete Consult the sections on filter pipelines section 3 2 and on filter results 5 4 2 2 for more info 4 8 Anti Virus Filter Setup Every virus checker that offers a command line interface can be integrated into CleanMail In the Anti Virus Filter Setup dialog you can easily adapt and test the operation of third party virus checkers The Anti Virus Filter Setup dialog is based on the External Filter Setup dialog See there for an explanation of settings not explained here To configure a virus filter CleanMail needs to know the vendor name You can set the scanner path in the Scanner Executable setting if you did not install your virus checker in its default location 27 CleanMail Anti Virus Filter Wizard EX Virus Checker Settings Integrate a third party virus checker for use with CleanMail Choose lt other gt if the virus scanner you want to use is not on the list of supported scanners See the vendor s documentation about command line scanner usage instructions Vendor Name Clamwin Free Antivirus If the virus scanner was installed into another directory than the default modify the scanner executable setting accordingly Scanner Executable C Program Files ClamWin bin damscan exe a
59. s filters into the SMTP POP3 checking pipeline These filter types are included in CleanMail Blacklist Whitelist Filter Blacklist and whitelists allow filtering based on the sender address of a message Delay Filter SMTP filtering only The delay filter has proven to be very effective against the bulk mailer software used by spammers DNSBL Filter The DNSBL filter also known as remote blacklist filter can get rid of spam messages at the cost of a few DNS lookups Attachment Filter The attachment filter can remove potentially malicious attach ments at very little processing cost SpamAssassin is a trademark of the Apache Software Foundation Windows is registered trademark of Microsoft Corporation Virus Filter CleanMail uses ClamVVin Clam Anti Virus to protect you from email borne viruses It also supports many third party virus scanners out of the box e g Computer Associates Anti Virus F Prot Anti Virus Kaspersky NOD332 just to name a few Virus mails are rejected and deleted by default SpamAssassin Filter SpamAssassin is the world leading open source spam filter Though it is one of the best spam filters around with a very good spam detection rate and only few false positives it processes mails only slowly and causes a rather high CPU load Spamtrap Filter SMTP filtering only This filter can be used together with Spa mAssassin to train the spam mail database Bayes database used by Spa mAssassin Mail Storage
60. s only zip and bmp attachments all else are blocked If a mail has a pif or scr attachment the attachment is not only blocked but the entire mail is deleted pif and scr are very common as virus vectors 4 3 2 Ignore Whitelist For security reasons anti virus filters and the attachment blocker by default ignore whitelisting You can change this behaviour by removing the check mark from the Ignore Whitelist setting 21 4 3 3 MIME Error Policy MIME violations can disrupt mail server operation and sometimes crash mail clients Also worm authors try to hide executable attachments with deliberate MIME syntax violations The attachment blocker is also capable of detecting MIME violations and you can choose which policy to apply for messages affected General MIME syntax violation SEVERE Worm authors could try to hide executable attachments with deliberate MIME syntax violations e ASCII 0 character SEVERE The mail contains an ASCII 0 character This problem can disrupt mail server operation and sometimes crash mail clients e Line Break Error The message has a single carriage return or line feed character in the message or a line is too long These MIME violations are very common in spam messages but also sometimes present in legitimate messages e 8 bit character in header This MIME violation is very common and for this reason only reported in the log For severe MIME violations we recommend deleting messages You can
61. sites has proven to be highly effective in identifying spam mails The result of all these tests is added up to form a spam score A message is con sidered spam if the score exceeds a configurable threshold You can modify the aggressiveness of the spam checker by modifying this threshold an aggressive set ting with a low threshold will find more spam mails at a higher risk of legitimate mails falsely identified as spam false positives In the typical configuration the subject of mail identified as spam is modified to flag it as spam mail and the message is quarantined within a SpamAssassin wrapper to prevent accidental infection with dialers spyware trojans or viruses by viewing HTML content Now it is up to your mail server or client software to decide what to do You can delete spam mails or move spam mails to a spam folder or leave the decision what to do with spam mails to your users 4 9 2 SpamAssasssin Options CleanMail SpamAssassin Filter Wizard Es SpamAssassin Settings Set required hits and subject tag for spam mails Set the threshold score required for a mail to be considered spam Smaller scores are more aggressive more spam is removed but at the same time false positives are more likely Required Score 4d Set the text added to the subject of mails considered spam The keyword _SCORE_ will be substituted by the calculated spam score for the message _REQD_will be replaced by the threshold value see above
62. ssag Fetching a message with the RETR command does not delete this message it still remains in the mailbox For deleting a message the DELE command is used 52 DELE 1 FOK message 1 deleted Hovvever POP3 servers do not actually delete messages until the session has been closed Interrupting a POP3 session for this reason may cause messages to be transmitted to the POP3 clients multiple times So in order to make deleting the message permanent the session has to be closed using the QUIT command QUIT OK Bye Connection closed by foreign host 7 2 2 POP3 commands USER Specify a mailbox or user name PASS The password for the mailbox LIST Lists messages in the mailbox RETR Fetch a particlar mail from the mailbox DELE Mark a message for deletion QUIT End POP3 session delete messages marked for deletion 7 2 3 Server replies POP3 server replies begin with a OK if no error occurred or with ERR in case Of an error 53 Chapter Licensing and Contact nformation 8 1 Ordering CleanMail For the latest pricing information please visit our CleanMail is distributed online electronically and shipped on CD ROM if re quested Please visit our to place your order online Ordering online and paying by credit card is by far the fastest way to order Your license key is usually delivered in a matter of minutes If you do not vvant to order online using your credit card vve offer a variety of alternative o
63. tachment Filtering Options CleanMail s built in attachment blocker allovvs you to specify a list of attachments that you vvant to accept or the other vvay round you can specify a list of attach ments you do not want to accept The attachment filter is pre configured to reject all attachment types known as potential virus vectors The configuration page allows you to enter attachment types in three input fields Settings in fields lower down override settings in the fields higher up You can use the wildcard characters any character and x any number of any character for example like in vbx CleanMail Attachment Filter Wizard es Ec Attachment Filtering Configure the attachment types you want to filter Configure the attachment types you want to filter You can use the wildcard characters 7 any character and any number of any character for example like in b Pass List pass attachments of this type Block List remove attachments of this type Delete List delete messages with attachments of this type bat chm cmd com cpl crt dll exe hip hta inf ins isp js ise Ink mdb msi msp nws ops ocx pcd pif prf reg rm rt sef ser sct shb shm shs shtm shtml url vb vbe vbs vbx vxd wsc wsf wsh List of attachment ty or more attachment Figure 4 1 Attachment Filter Setup Here is an example Pass Attachment List zip bmp Block Attachment List x Delete Attachment List scr pif This passe
64. the program will be used If you ve enabled filter error logging see Global Settings section4 1 3 the stan dard error output of a program is collected and printed to the log Instead of piping the message through standard input or output you can use the placeholders 6105 SOUT and SERRS as arguments to a program Here is an example c dir clamscan exe SINS mbox no summary Notes Be sure to use double quotes where needed If your temporary directory path for example contains blanks 5 IN must be quoted because the filter input and output files reside in the temporary directory The working directory of external programs always is the CleanMail installation directory To test your settings with a sample spam mail or a sample virus mail use the test buttons provided 4 7 1 2 Batch Files You can also run batch files instead of running a program Depending on the Win dows version you are using 1t may be necessary to explicitly run a command line 25 Test Filter folaJEs Input Output Received from byteplant com 1213 239 200 169 Received from localhost by User PC by localhost 1127 0 0 1 with SpamAssassin version 3 2 4 with SMTP Wed 15 Sep 2004 15 31 22 0200 Sat 06 Dec 2008 14 08 30 0800 Subject Test spam mail GTUBE From Sender lt sender example net gt Date Wed 15 Sep 2004 15 31 22 0200 _ To Recipient lt recipient example net gt From Sender lt sender ex
65. tting a very large message Allowable values are 10485760 10MB to 1048576000 1000MB the default is 20971520 20MB MaxLogFileDays numeric The log file is cycled after so many days Set to 1 by default daily log file cycling both unsetting this value or setting it to 0 disables this feature MaxLogFileSize numeric The log file is cycled once it is larger than the given size Allowable values are 1048576 1MB to 1048576000 1000MB the default is unset disabling this feature MaxMemoryUsage numeric A load factor determining cleanmail s memory us age The default value is 0 8 allowable values are in the range between 0 to 1 PreferEnableFilter boolean Determines cleanmail s filter behaviour if a mail is addressed to multiple recipients Defaults to true in this case a filter is applied if the filter is enabled for at least one recipient and not applied otherwise If set to false a filter is not applied if the filter is disabled for at least one recipient and applied otherwise StatisticsTimeFrame boolean Sets the number of days how long statistics data is kept Defaults to 365 allowable values are in the range of 7 one week to 10000 about 30 years 7 1 4 Port Settings The session manager section may contain multiple proxy port subsections Clean Mail supports different types of proxy ports with the port type determined by the section label All types of proxy ports have several settings in commo
66. ults 423 Subject Tag a airea a ee sa A y 4 3 Attachment Filter Setup 4 3 1 Attachment Filtering Options 4 3 2 Ignore Whitelist 4 3 3 MIME ErrorPoliey 4 4 Blacklist Filter Setup 4 4 1 Sender Address Patterns 442 POll Vi de e das gi s n lir 4 5 Whitelist Filter Setup 4 5 1 Sender Address Patterns 4 6 RBL Filter Setup 4 6 1 DNSBL ZoneList 4 0 2 PONCY scada A Alay a BEY Ms B D R qs 4 6 3 Relay Check Option 4 7 External Filter Setup 4 7 1 CommanmdLine 4 7 1 1 Message Text Input and Output 4 7 1 2 BatchFiles 4 7 2 Advanced Settings 4721 Timeout x su a Sed oa XD a a 4 7 2 2 Ignore Whitelist 4 7 2 3 Skip SiZ s 2 25 22 24 2d AT be eee a 4 7 24 Memory Usage 47 3 Return Code Policy 4 8 Anti Virus Filter Setup 4 9 SpamAssassin Filter Setup 4 9 1 How SpamAssassin Works 4 9 2 SpamAssasssin Options 4 9 2 1 Required Score 4 9 2 2 Subiect Tag 4 9 2 3 Tweaking The SpamAssassin Rule Set 4 9 3 CleanMail SpamAssasssin Options 4 9 3 1 Spam Mail
67. y moved to the best position in the filter pipeline Afterwards you can still change the order of filters but only within limits You can also move filters as you please though we do not recommend it by editing the configuration file with a text editor see CleanMail Configuration File section 7 1 16 Chapter 4 Configuration CleanMail is usually minimized displaying a small icon in the system tray usually in the lovver right corner of the desktop By right clicking this icon you can pop up a menu to maximize CleanMail giving you access to the configuration dialogs Note Depending on its configuration Windows XP sometimes hides this icon To make the CleanMail icon reappear click on the arrow symbol left of the system tray Within the configuration dialogs you can freely step forward and backward using the Next and Back buttons You can cancel your changes anytime by pressing Cancel Once you pressed Finish your changes become permanent and are stored in CleanMail s configuration file cleanmail cf Important Once you have saved new settings they are not yet in use by the Clean Mail service To make the service re read the configuration file choose Apply Settings from the file menu once you are ready 4 1 POP3 Proxy Port Setup POP3 Proxy Port Setup dialog is invoked by choosing Global Settings from the file menu or by double clicking the POP3 proxy port information on the con
68. you to configure tvvo aspects of Spa mAssassin filters e A plugin part that controls to what messages the filter is applied and what is done with a mail once it is tagged as spam filter policy section4 2 2 The settings in this part are stored in the cleanmail cf file e Configuration of SpamAssassin itself The settings in this part are stored in the file Local cf in the SpamAssassin rule set directory It is important to remember this especially when you are planning to use multiple SpamAssassin filters section4 9 3 2 in your configuration 4 9 1 How SpamAssassin Works SpamAssassin is a well known open source spam detection engine It uses the following techniques to identify spam e The mail headers are scanned for some small inconsistencies that can give away forgeries A mail date in the past or in the future forged message IDs and the like e The mail body is scanned for typical spam mail content such as spam key words capitalized letters or invitations to buy or click something e Queries to blacklist servers are used e g to see if a mail has been submitted from a known open mail relay 29 e Probability analysis of mails Bayes filtering Spam mails can be trained so that similar mails are more likely to be identified as spam in the future e Analysis of the URLs a mail refers to Spammers want you to click on hy perlinks referring to their sites so a lookup in a database of known spam advertised

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