Quote:
but with other mail-processing software

Postfix supports delivering to maildir just fine. Procmail also works well, and has the advantage of being able to process multiple messages with file locking out of the way. Grepmail, never personally used, but mairix offers the same features on maildir files. Spamassassin has a learning mode and can learn from messages in a maildir folder.

I do enjoy that rm works to delete a message, and mv ../new can mark it unread again. For me, I moved to maildir the same time I implemented IMAP, so the transition was easier.