Procmail Filtering - Stop unwanted spam and viruses

As email arrives for a user, it is passed onto the user's ~/.procmailrc file (if it exists). You can process/filter your email with "procmail recipes". "man procmailex" on unix machine for many examples. procmail.org has wonderful links, including http://pm-doc.sourceforge.net/pm-tips.html.

SpamAssassin

• CSE Email server now supports SpamAssassin.

Benefits of procmail

• Automatically sort email based on subject, sender, recipient
• filter spam
• Train SpamAssassin to detect spam
• optionally deliver your email directly to a folder in your home directory so you no longer have to deal with "Mailbox too large" warnings.

Sample ~/.procmailrc file

------- cut here --------------
PATH=/bin:/usr/bin:/usr/bin
MAILDIR=$HOME     #you'd better make sure it exists
#DEFAULT=$MAILDIR/MailBox     #completely optional
LOGFILE=$MAILDIR/from     #recommended
#VERBOSE=yes     #added logging
SPAMASSASSIN=spamassassin

# delete any email with Flame in the subject (send it /dev/null)
:0
* ^Subject:.*Flame
/dev/null

# filter email with spamassassin, tagging spam with an extra header
# Option added to not check files with large attachments. Those are
# rarely spam and can be too much of a load on our mail server.
:0fw
* < 256000
| $SPAMASSASSIN -L

# if spamassassin labels email as spam, then filter it (move to Mail/junk)
:0:
* ^X-Spam-Status: Yes
Mail/junk

#otherwise, go to your mailbox
-------- to here ----------------

A more advanced promail file can be found here.

Also learn how to train spam assassin here.

What does SpamAssassin do?

Procmail will filter email through spamassassin. Spamassassin works on a threshold point system. Certain spam characteristics are awarded a point number. If the point values exceeds a threshold, spamassassin will insert an X-Spam-Status: Yes in the headers. You then have procmail filter those to a spam folder or /dev/null Spamassassin also creates a ~/.spamassassin directory where you can define other configuration options.