To enable SpamAssassin (as preconfigured in the standard RedHat 9.0 distribution) on a user by user basis, add the lines
:0fw: spamassassin.lock | /usr/bin/spamassassin
to .procmailrc in your home directory (assuming that sendmail is configured to use procmail as the local delivery agent). The incoming spam should then be tagged (X-Spam-Flag: YES) and the subject line should be changed to include [SPAM]. Personal preferences can be found in .spamassassin.
A better strategy for large-scale deployment would be to replace /usr/bin/spamassassin above with /usr/bin/spamc (which might need the spamd daemon running). But we'll leave this for the future.
© M. Vallisneri 2012 — last modified on 2010/01/29
Tantum in modicis, quantum in maximis