Hei, Recently I am thinking of reimplementing our MX servers. Of course rcpt check is a must, also I should not generate NDRs later, I should only accept mails from outside which won't cause bounce on the mail store MTA later. My problem: there are some conditions cannot be forecasted easily, I can't be sure that mail can be delivered (over quota, user is deleted between the moments of mail at MX and the mail storage etc). Some people would say, that this issue is minor, and quite rare so I should not care about this. However I think even rcpt checking can be eliminated on MX servers if I have some kind of SMTP proxy like thing (instead of "real" MTA with queue) at the MX servers. Since mail store won't accept the mail for non-existing rcpt address, an SMTP proxy like solution does not even need rcpt check itself. Also the over quota problem is solved. Also, I hate when there is some rare problem with the backend mail servers (mail stores) and we have huge queues filled up with waiting mails, I would say, that MX servers shouldn't accept anything if they are not 100% sure that they can transfer the mail to the backend. Since MTAs should have queue anyway, I am not sure this kind of SMTP proxy server can be implemented with postfix (it would be great since I would be able to use its policy server and maybe milter too), the key feature that it shouldn't use any queue, when sender MTA issues the corresponding SMTP commands, it should do that for the backend and giving back the result. What do you think, is it a bad idea? I know this is really not like a traditional MTA, should I use some kind of SMTP proxy solution instead then? Any idea? Thanks a lot.
-- - Gábor
