Have just upgraded to RedHat 6.0 from RedHat 5.2 and procmail processing has stopped working. The security improvements in procmail stop $HOME/.procmailrc files being read from group writable directories However, out-of-the box, RedHat has User Private Groups and a umask of 002. Procmail complains, and won't read the .procmailrc file, resulting in no processing. UPG is secure (ish), but procmail can't distinguish between a secure setup with group writable dirs and an insecure one. See related problem with sendmail. I'll be happy to continue discussion of this problem by e-mail.
Fixed in procmail-3.13.1-4 and later ; available in rawhide. Will be integrated in the next release