Hi, I have thought a while, if I can ask that here, but as it just is a technical question, I hope you understand that I am just interested to understand something and not to make another feature request. So with respect to your time:
As an example, we have smtpd_proxy_filter. From my understanding that receives a mail and hands it over to a real time content filter that should be designed to return the mail afterwards back into postfix. I guess that is, because of cleanup, trivial-rewrite and qmgr and stuff. As more and more system are not the final destination in terms of moving a received mail directly into a Maildir folder or calling procmail/maildrop, they use LMTP to connect to Cyrus or Dovecot (simplified spoken). So the mail is received and cleanup/trivial-rewrite, qmgr are doing their jobs. After that LMTP is called and Postfix tries to "relay" it over to i.e. Dovecot, which might have sieve active or quota. In both cases it could be a problem, if Dovecot rejects the mail (not temp failures). I hope my understanding was right so far. Would it technically possible to have a smtpd_to_lmtp_proxy option (or however it could be called), that would receive on smtpd and open a connection to its LMTP server, doing cleanup and Co. in memory and wait for the result of the LMTP server? If the LMTP process gets 250 OK, postfix would give that back to the client. Else closing the session with error status code received from the LMTP server. RFC2033: … 3. Introduction and Overview … This queuing requirement is beneficial in the situation for which SMTP was originally designed: store-and-forward relay of mail between networked hosts. In some limited situations, it is desirable to have a server which does not manage a queue, instead relying on the client to perform queue management. As an example, consider a hypothetical host with a mail system designed as follows: … Positive aspects: - sieve reject being no problem - over quota bounce - speed If I understood LMTP correctly, we would have a problem with recipients that produce a failure. How would the SMTP session behave? I don't know, how Postfix is doing this at the moment. Furthermore using some kind of smtpd_to_lmtp_proxy would mean not to use qmgr, as we would not queue the mail on persistent storage. Is that right? I am far away from being an postfix expert, so this is just trivial thinking about something that might be extremely complex to accomplish. And I am always willing to learn and to understand :) Thanks for reading. And thanks in advance for an answer. Kind regards -Christian Rößner -- [*] sys4 AG http://sys4.de, +49 (89) 30 90 46 64 Franziskanerstraße 15, 81669 München Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263 Vorstand: Patrick Ben Koetter, Axel von der Ohe, Marc Schiffbauer Aufsichtsratsvorsitzender: Joerg Heidrich
