On Sun, Nov 10, 2013 at 12:59:27AM +0100, Reindl Harald wrote:
everywhere else you have sender-dependent relay hosts, RCPT dependent relayhosts and all sort of aliases which you *do not* want treated different between incoming mail from outside or a internal server and submission mail
the only real difference between submission is that it is authenticated and because the authentication a few restrictions are not applied
I don't quite agree. Our "smarthosts" has very little local knowledge about where to route messages. They only follow MX records. It's the incoming SMTP servers that has all the knowledge, and needs to be robust against millions of broken mailservers and spam-bots on the internet.
The fact that submission is authenticated is an opportunity to integrate better with the userdb than postfix and exim does. To have native quotas, brute-force protection, per user geo-blocking, etc.. that are difficult to achieve with the general SMTP servers.
but in usual there is and must not be any difference in the mail-routing
Incoming SMTP servers routes to dovecot-LMTP, internal exchange, and more. Outgoing would only need to follow MX (even for messages heading back home to us).
-jf