The best replacement for procmail is maildrop.

The best alternatives to procmail are rated as following:
★★★★★  maildrop
★★★  sendmail
★★★  dovecot
★★  sieve
★  exim
  procmailrc

Your alternative for procmail is not listed? Suggest!
Speaking about procmail, one probably shouldn't forget about maildir.

Other search terms related to procmail and their ratings are:
★★★★★ maildir
★★★ postfix
★★ qmail
★★ spamassassin
★ fetchmail
You have in mind a companion for procmail and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of procmail in all years. Click on graph for more.
procmail
maildrop
sendmail