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Table of Contents

1. The New Mailhost
1.1. Current Anti-Spam Measures
1.2. Anti-Spam Measures on the New Mailhost
1.3. The Spam Settings Web Interface:
1.4. References

1. The New Mailhost

The new mailhost will be installed on Saturday, January 7, 2006. Expect TCC mail services to be down from 8:00 AM to 5:00 PM during the upgrade.

Most services of the new mailhost can be accessed the same way. Receiving and sending mail using webmail, mutt, pine, thunderbird, etc, will work the same as before. What is changing are a lot of the internals, mainly the anti-spam system.

Updated System Packages:

  • SquirrelMail (webmail.nmt.edu) has been upgraded to version 1.4.5 from 1.4.3a

  • Spamassassin has been updated to version 3.1 from 2.6

1.1. Current Anti-Spam Measures

Our current anti-spam measures block spam via several mail filters, DNS Blacklists, Spamassassin, and McAfee anti-virus. This aggressive anti-spam system leads to false positives (mail that is not spam, but is being blocked as spam).

However, with the emergence of new spam methods, and the constant increase in spam volume, the aging system is losing effectiveness in spam blocking.

1.2. Anti-Spam Measures on the New Mailhost

The new spam system is based on tagging, not rejection, to greatly decrease the number of false positives. The new system is designed to allow for easy upgrades for anti-spam packages such as Spamassassin, to stay current with new spam trends.

The new anti-spam system provides you two methods that you can use to block spam:

First are whitelists and blacklists. A whitelist consists of a list of email addresses you know are not spammers, and you always want their mail to reach you. A blacklist is a list of email addresses you know to be spammers, or that you never want to receive mail from. You will be able to set these through a web interface, https://webmail.nmt.edu/spam/index.php

If the address was not in a whitelist or blacklist, then the mail will be scanned by Spamassassin. Spamassassin will assign a "spam score" to your mail, which the anti-spam system will evaluate. You can set a threshold level at which mail will be marked as spam.

The threshold you can set is the tagging level. When your mail's "spam score" reaches above this level, a tag, unseen in the body of the mail you receive, will be added to the mail's header. Also the subject of the mail will be prefixed with ***SPAM***. The lower the spamassassin score, the less likely the mail is to be spam. Scores around 4 and below are usually not spam. In webmail, when viewing a mail, click on "View Full Headers." Here there will be a line that begins with "X-Spam-Status:" This line will tell you the spam score, and which tests contributed to that score. Using this you can gauge what scores your mail are receiving, and adjust the level accordingly. The tag added by this threshold will be used to filter the spam out of your Inbox into a spam folder using procmail.

  • If you have never setup a .procmailrc file in your account, during the upgrade one will be created for you in your home directory. The procmail program will use the instructions in .procmailrc to filter spam tagged by the second threshold into a SPAM folder, called username.spam, where 'username' is your TCC username.

  • If you have procmail setup for your account, the following recipe can be added to filter spam:

    # Catch SPAM
    :0
    * ^X-Spam-Flag: YES
    $HOME/$LOGNAME.spam
    

    Then create a soft link to /fs/tedium/spam/username.spam at ~/username.spam, where 'username' is your TCC Username. This file will not count as part of your disk quotas, and mails in it will be cleaned out after 30 days. Then subscribe to that folder in IMAP.

All mail will be tagged by spamassassin by default. If you do not want your mail tagged, file a ticket at http://infohost.nmt.edu/~ticket/

1.3. The Spam Settings Web Interface:

A screen shot of the spam settings page, this will be accessible from https://webmail.nmt.edu/spam/index.php on the new server. The spam threshold is set to 4.5, this is the level mail will be classified as spam. There are two entries in whitelists, which mail will always be recieved from. Mail from spammer@spam.net will never be received because that address is in the blacklist.

1.4. References

Here are some links about spamassassin, and procmail.