I am surprised that there are so little open-source solution for this very common need in corporate environment.
The first that slips mind are Postfix’s bcc_maps directives (or similar). Alternative mechanism should be pretty straightforward – thru milter system. If someone reading this post finds some other useful utility (open source only), please post a comment about it.
And, my list f sound open-source solutions is:
- Postfix’s recipient_bcc_maps (mails send to some adresses) or sender_bcc_maps (for mails sent by some user addresses)
- Open Mail Archiver (I really like the straightforward idea)
- Scam-archiver
- MailArchiva (Open Source Edition)
- Or maybe some procmail recipes like here or Æmail