Sendmail

Spam and Virus Filtering Con't

Step 10: Spam Management and Removal (optional)

Up until now your Spam Filter is really just Spam Tagging, Spamassassin does not delete messages. All messages are still being delivered to the INBOX, but a Spam Flag is Added (with values of yes or no) and a Spam-Level tag is added providing the score (A higher score means that it is more likely to be spam). Any modern Mail Client should be able to read the Spam Confidence Level (Score) on the tags and perform the necessary action. However if you are providing webmail or have IMAP clients you might want to set up the server to sort or delete the obvious spam. To do this you must edit /etc/procmailrc

INCLUDERC=/etc/mail/spamassassin/spamassassin-default.rc

#This allows SpamAssassin to use the main Bayesian DB
DROPPRIVS=yes

# SpamAssassin sample procmailrc
#
#
# The condition line ensures that only messages smaller than 250 kB
# (250 * 1024 = 256000 bytes) are processed by SpamAssassin. Most spam
# isn't bigger than a few k and working with big messages can bring
# SpamAssassin to its knees.
#
# The lock file ensures that only 1 spamassassin invocation happens
# at 1 time, to keep the load down.
# This should already be in /etc/mail/spamassassin/spamassassin-default.rc
# Uncomment if it is empty or non-existent.
#
# :0fw: spamc.lock
# * < 256000
# | spamc

# Mails with a score of 15 or higher are almost certainly spam (with
# 0.05% false positives according to rules/STATISTICS.txt).
#Let's delete them. (This one is optional)
#WARNING- this turns on spam deletion!
#If you have any false positives these messages are not retrievable!
#Each \* Represents one point, to make deletion more sensitive change
# the number of \*. Right now you can see that there are 15 of them.
:0:
* ^X-Spam-Level: \*\*\*\*\*\*\*\*\*\*\*\*
/dev/nul

# All mail tagged as spam (eg. with a score higher than the set threshold)
# is moved to "spam".
:0:
* ^X-Spam-Status: Yes
Spam

# Work around procmail bug: any output on stderr will cause the
# "F" in "From" to be dropped. This will re-add it.
:0
* ^^rom[ ]

Step 11: Turn on the Spam Services

service sendmail stop
chkconfig sendmail on
chkconfig clamav-milter on
chkconfig spamassassin on
chkconfig spamass-milter on
service clamav-milter start
service spamassassin start
service spamass-milter start
service sendmail start

Step 12: Check your Logfiles for Errors

tail -n 30 /var/log/maillog
tail -n 30 /var/log/messages

Your Sendmail server is now Rockin'!

Troubleshooting Your Spam Configuration

References:

Sample Sendmail configuration file

Spam proof and Virus Filtering e-mail server -
http://www.centos.org/modules/newbb/viewtopic.php?topic_id=4938

Centralized Spam Filtering:
http://www.stearns.org/doc/spamassassin-setup.current.html#sitewide

Spam Assassin Configurator:
http://www.yrex.com/spam/spamconfig.php

Article last reviewed: 12/29/2006

Created by: Digital Foundation, inc.

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