Procmail

Procmail is an autonomous mail processor.

It can be invoked at the individual user level simply by placing the following text inside of $HOME/.forward

"|exec /usr/local/bin/procmail || exit 75"

note the above must include the absolute path to procmail. After that, now you can begin the fun by creating a .procmailrc Here is a sample .procmailrc that assumes you're using Maildir format instead of mbox, and your Maildir folder is $HOME/.maildir/:

CLEAN=${HOME}/.maildir/
PATH=/usr/bin:/bin:/usr/local/bin:.
MAILDIR=${HOME}/.maildir/
LOCKFILE=${HOME}/.lockmail
LOGFILE=${HOME}/.maillog
DEFAULT=$MAILDIR
# This places any emails To or Cc *gwbush* into the ether.
:0:
* ^(To|Cc):.*gwbush*
/dev/null
# The following are examples for a few popular mailing lists, in which it will
# place the content into the folder prefixed with .
:0:
* ^Sender:.*yashy-hack@mail\.yashy\.com
.yashy-hack/
:0:
* ^(To|Cc):.*nmap-hackers@insecure\.org
.nmap-hackers/
:0:
* ^Subject:.*Politech*
.politech/
# Garbage filtering
# B = Body 
:0
* ^Content-Type: multipart/alternative
* B ?? ^Content-Type: (audio/x-|application).*;.*$.*name=.*\.(scr|com|bat|pif|lnk|exe)$
.klez/
:0
* ^Content-Type: multipart/mixed
* B ?? ^Content-Type: (audio/x-|application).*;.*$.*name=.*\.(scr|com|bat|pif|lnk|exe)$
.yaha/
# This is if size is greater than
:0
* > 98400
.bigfile/