[Dovecot] Multiple delivery with LDA+sieve

Hi !

I am still a bit annoyed with the way that Sieve plugin handles multiple delivery into the same folder.

For reference : http://www.dovecot.org/list/dovecot/2007-January/019029.html

Summary : When a same message (same message-id) is to be delivered twice into the same mailbox, it is delivered twice while I think that the second one should be discarded.

Here are a few test cases :

• you subscribe to a few mailing lists on topic "X" and deliver all mails from those mailing lists in the same folder. You get twice the mails that are crossposted.
• you subscribe to one mailing list and read it regulary so you don't care of receiving messages from this mailing list (you are in Cc when someone answers) in your INBOX. You match on To or Cc to put everything in the same folder. You get messages twice when you are put personally in Cc.
• you place a forward from one account to two of your accounts (one is keeping backup, the other don't but delivers faster). You receive all messages twice.

With procmail, I handle those (real) cases with formail. I can't with Sieve. I don't see any interest in receiving the same message twice into the same mailbox. Is it possible to maintain a list of recent message-id and mailbox couples to avoid to deliver again a message to the same mailbox ?

Terminate input by end-of-file or marker, not by count. - The Elements of Programming Style (Kernighan & Plauger)