What it is
Everybody wants their spam to die. This short little jobbie can be copied into your .cshrc.mine file on Athena to filter and delete spam automatically from MH. You should have this dot-file already, but if you don't it is easy to create one by typing emacs .cshrc.mine at the Athena prompt, adding these lines to the new file, then saving and quitting with ctrl x s x c (keep control down, type the letters one after the other).

alias inc '/usr/athena/bin/inc +inbox; \\
pick -sequence spams --x-spam-flag YES && \\
(echo ; echo "Shredding useless documents...:" ; \\
scan +inbox spams; \\
rmm spams)'

How it works
alias inc redefines "inc" to mean "inc, but use the following so I'm not subjected to porn or tempted to be a good samaritan to those poor Nigerians." It picks emails that come into your inbox, and if they have the --x-spam-flag YES will decide they are spam. Echo will relist the mails it considers spam, so false positives can be identified (I haven't had a single one yet). It then scans that list and deletes (rmm) those positively identified.

The \\ means that the action continues on the next line. The echo message in the quotes can be changed - this is your chance to be creative. Any false positives can be undeleted and returned to your inbox by going to the inbox (usually, cd ~/Mail/inbox, then undelete messagenumber).

Other
SpamAssassin takes a swipe at junk e-mail
Why am I getting all this spam?