[ On Tuesday, December 9, 2003 at 21:31:47 (+0000), Russell King wrote: ]
> Subject: Re: [Exim] Domain literals: weighing up the arguments
>
> That's debatable. Does it (or some other server) provide mail service
> for those domains? If not, they aren't valid mail domains, so why
> should postmaster@randomhostaddress be valid?
>
> If you're going to say "well, it runs a SMTP server" what about a host
> which only ever delivers mail, but never accepts mail?
If it runs an MTA and makes outgoing SMTP connections but never listens
for incoming SMTP connections then it doesn't run an SMTP server.
However if it runs an SMTP server then it almost certainly accepts mail!
Look, this isn't very complicated and it really shouldn't take genius to
be able to figure out which e-mail addresses, and in particular which
e-mail addresses using the "postmaster" local-part, that any and _every_
MTA really Really REALLY _SHOULD_ accept.
For example if any MX record has "randomhostaddress" as its target name
then clearly "randomhostaddress" is a hostname of an SMTP sever that is
expected to accept mail and both <postmaster@randomhostaddress> and
<postmaster@[N.N.N.N]> where "N.N.N.N" is the address that the A record
for "randomhostaddress" points to.
Also, given the very simple rules one can trivially derive from that
example, and given the larger picture of how SMTP MTAs route and deliver
e-mail to their peers, it should be abundantly clear to anyone who
thinks it through that any mailer which answers SMTP connections on the
IP address N.N.N.N and which normally accepts e-mail for one or more
domains, really _SHOULD_ also accept <postmaster@[N.N.N.N]> and indeed
_should_ also treat every local mailbox as valid when it has a
domain-part of "[N.N.N.N]".
Now can we please eliminate from this discussion at least all of this
complete nonsense about random IP addresses and whether or not every
host reachable by IP has to accept SMTP connections and so on? We're
supposed to be talking only about mailers that accept mail by way of
SMTP and not about terminal servers, PDAs, toasters, and other
non-mailer "hosts".
If you want to ping your desktop telephone or your networked eyeware
with IP then that's fine but please leave it out of this conversation
because we're not talking about it!
I think everyone was very well aware long before this thread started
that a host can make an outbound SMTP connection without running an SMTP
server and without being forced to accept mail to its local postmaster
mailbox. However the whole point here is that IFF you're going to run a
mail server on a host then you REALLY _SHOULD_ make it easy for your
peers to communicate with you even when the DNS is totally FUBAR, and by
convention the best and most obvious and most widely expected way to do
this is to accept mail for <postmaster@[N.N.N.N]> where "N.N.N.N" is an
IP address your mailer listens for SMTP connections on.
--
Greg A. Woods
+1 416 218-0098 VE3TCP RoboHack <woods@???>
Planix, Inc. <woods@???> Secrets of the Weird <woods@???>
