> > And i know you all keep politely telling me im crazy for not > understanding postfix wants to deliver to user's mailboxes. I get that. > Not knowing the inner workings of postfix, from a logical point of view, > submission isn't smtp:25, it has its own service spawn, it works on its > own port, so it didn't seem crazy to expect it to be able to behave > differently than smtp:25.
Think about postfix as about some kind of router. It has several "input channels" like smtpd server or sendmail command. All messages go to the queue and routed by "qmgr" regardless the way they got to the system http://www.postfix.org/OVERVIEW.html I also like this picture from the Wikipedia (but the generic(5) table is missing there for some reason) https://en.wikipedia.org/wiki/Postfix_(software)#/media/File:Postfix_architecture.svg "smtp:25" is not a different postfix, it is just one more "input channel" > I at first didn't understand that it has to > use the same setting values that smtp:25 uses. I mean, logically that > being the case, what is the point of having a separate submission on > port 587 when smtp:25 could just "answer the call" if all of the > settings are the same between the two? > permissions may be different. You can filter incoming calls on 25 but not on the submission port. It is not uncommon to see things like -o syslog_name=postfix/submission -o smtpd_client_restrictions=$mua_client_restrictions so, we have different restrictions for mua (client here). "smtp:25" is your front door. "submission" and "sendmail command" are backyard doors. All of them are used by email to "jump" into the Postfix, but "front door" (25) is used by foreign visitors and has strong security policy) > >
