I have an RHES3 system with sendmail 8.12.11-4 and qpopper4.0.5. I can't upgrade to the latest version of sendmail because I depend on rpm updates, and when I've tried installing the latest version of programs from source I've run into problems that are too hard to fix. Given that my sendmail config already blocks RBL sites, my junk mail consists of mail from mostly legit-looking addresses (all of them different, so I can't block them with sendmail's access database), so I tried writing recipes/filters to block unwanted commercials in procmail, which is the school solution to this problem, along with spamassassin. The procmail filters work for my root account, however I'm looking to block spam for all the accounts I host on my server with one set of rules, and procmail doesn't lend itself to that. I found a page that talks about invoking a procmail ruleset directly from sendmail at http://www.professional.org/procmail/mailer.html
, however I'm warned that any mail addressed to my server may disappear if I screw this up, so I'm looking for more advice before proceeding.
Fyi, I have a backup Debian server with Postfix on it and a mail account for a user that's aliased to root, so I could try working on that one first, but I'd have to replace Postfix with Sendmail to get a more approximate demo, and the last time I tried working with sendmail on Debian (ubuntu), there were significant differences between that version and the one I have on my Redhat system, so I'm not sure how helpful it would be. I'd have to be careful about version numbers of course, but I was pretty sure I installed the same version on Ubuntu that I have working on my RHES.