Given a pair of postfix instances, one "out front" to be a relay (MTA), the other "behind" to host mailboxes (MDA)
How do we get the MTA to relay incoming mail to the MDA ? SMTP or LMTP or …? Mail sent to the MTA is looking for a "local recipient". Then the same question for outgoing mail from MDA to MTA to final destination. Our dilemma is that most online tutorials and how-to's have everything on one server.
