IOW: Which of the following are required vice recommended vice best practives, etc.
a) postmaster@example.com b) postmaster@mail.example.com c) postmaster@wizzbang.example.com d) postmaster@pop.example.com e) postmaster@cisco.example.com
and most important to me: where to I go to justify the decisions on same?
2821 (section 4.5.1) says that "postmaster" (with no domain" must be accepted as: (a) a local name (with no domain specified, as in: RCPT TO:<Postmaster>" (b) A mailbox at every domain for which the mail server accepts mail. That means that the answer to your five questions are are: a) postmaster@example.com is required if any mail addressed to @example.com is accepted. b) postmaster@mail.exam is required if any mail addressed to @mail.example.com is accepted. c), d), e) follow the example above. Had you also included: f) postmaster The answer would be "yes, that is required". RFC2821 would be a good place to go to justify decisions on same. (Well, to justify a decision to implement postmaster@any.domain.for.which.mail.is.accepted, and to implement "postmaster". It wouldn't really help you justify a decision to not implement that. OTOH, if someone is arguing that the the mere existance of xyz.com implies that postmaster@xyz.com must exist, then I would note that neither RFC2821 nor any other RFC of which I am aware imposes such a requirement. As long as @xyz.com isn't being used for any mail, there is no requirement for postmaster@xyz.com to exist.) -- Brett