Message-Id: <199510052105.RAA02108@wilma.cs.utk.edu>
From: Keith Moore <moore@cs.utk.edu>
To: Harald.T.Alvestrand@uninett.no
cc: Robert Elz <kre@munnari.oz.au>, drums@cs.utk.edu, moore@cs.utk.edu
Subject: Re: support for Postmaster address 
In-reply-to: Your message of "Thu, 05 Oct 1995 13:37:29 BST."
             <199510051238.IAA13049@CS.UTK.EDU> 
Date: Thu, 05 Oct 1995 17:05:39 -0400
Sender: moore@cs.utk.edu

> After reading your arguments, and especially in light of the 521 MX
> discussion, I think the requirement for MX targets should be a SHOULD;
> there are valid cases where it's sensible not to do it, but most of the
> time, it's better if you do it.

Yes, I'm inclined to agree that SHOULD is better.

> BTW, RFC 1123 states:
> 
>          A host that supports a receiver-SMTP MUST support the reserved
>          mailbox "Postmaster".

So to revise my suggestions slightly:

+ for any domain that originates mail, postmaster@domain must be a valid
  and reachable address, even if 'domain' doesn't correspond to an actual
  host and is only listed as a mail exchanger RR in the DNS (even a wildcard 
  RR)

  (this is a requirement on system administrators, not SMTP implementations)

+ for any SMTP host that receives or relays mail, 
  <postmaster@fqdn.for.that.host> and
  <postmaster@[any-ip-address.of.that.host]> must
  be valid and reachable addresses, where fqdn.for.that.host is any
  domain name that may appear in a Received header for mail relayed or
  received by that host.

  (this is a requirement on system administrators, not SMTP implementations)

+ an SMTP server that receives or relays mail and connects directly to the
  global Internet must check to see that (a) it knows the FQDN of its host,
  and that (b) the addresses <postmaster@fqdn.for.that.host> and
  <postmaster@[ip-address.of.that.host]> are 
  routable, that is, there must be either a mailbox or an apparently
  valid forwarding address for the postmaster.

  (this is a requirement on SMTP implementations)

Keith