Errors-to: owner-drums@CS.UTK.EDU
To: "Roger Fajman" <RAF@CU.NIH.GOV>
Cc: drums@CS.UTK.EDU
Reply-To: kre@munnari.oz.au
Subject: Re: support for Postmaster address 
In-Reply-To: Your message of "Sat, 23 Sep 1995 23:40:16 EDT."
             <199509241029.GAA12979@CS.UTK.EDU> 
Date: Sun, 24 Sep 1995 21:06:33 +1000
Message-Id: <20115.811940793@munnari.OZ.AU>
From: Robert Elz <kre@munnari.oz.au>

    Date:        Sat, 23 Sep 1995  23:40:16 EDT
    From:        "Roger Fajman" <RAF@CU.NIH.GOV>
    Message-ID:  <199509241029.GAA12979@CS.UTK.EDU>


    This is the case that the proposed SMTP 521 (I think that's the number)
    reply is supposed to handle -- a host that doesn't accept mail at all.
    It explicitly says that accepting mail to postmaster isn't required,
    since the host doesn't really support mail.  There's an I-D on it under
    the mailext WG.

Thanks for the pointer - I hadn't looked at that.  Now I know this
is wrong, and off target, but as it was mentioned here (and mailext
I haven't been following), I am going to post this here and hope
that some mailext people are watching...

The "postmaster not required" in the draft applies only to hosts
that send 521 as the greeting code.   As a technique that would
be fine - except the draft says that it cannot be the target of
an MX, that is, every host that you don't want to receive mail
for has to actually implement this (trivial) SMTP server for itself.

Long term that is probably something to aim for (X terms, routers,
terminal servers, ...) all implementing this dummy SMTP server.
Unfortunately, that is not going to hapen overnight.

Consequently, the other approach, of MX'ing mail to a mailer that
bounces all mail is the only one we can use in practice today.
The 521 draft doesn't say that this MX target need not support
postmaster (though it does imply that its acceptable to say 521
to all addresses at a particular host - which would imply
postmaster as well, perhaps).   The implication seems to be that
this might be implemented by adding a list of bogus mail hosts
to a regular mailer, and sending 521 replies to the bogus domains,
but accepting other mail.  That wasn't my approach, the mailer I
described never accepts anything, a 521 greeting (once accepted)
would be a fine way for it to operate, except I really want it to
be an MX target for all of the dozens of boxes I have that have
IP addresses (A records) but to which mail should never be sent.
I simply can't install 521 SMTP servers in all of those things
(some don't even support TCP).

kre

ps: please do not reply on this to the drums list, take it to
mailext, or reply to me personally.