Re: RFC 2476

From: Ronald F. Guilmette (no email)
Date: Wed Oct 31 2001 - 13:54:57 EST

In message <>,
Ralf Hildebrandt <> wrote:

>On Wed, Oct 31, 2001 at 09:33:42AM -0800, Ronald F. Guilmette wrote:
>> I'm trying to find out if Postfix currently supports (conforms with)
>> RFC 2476, `Message Submission'.
>In German we say "Überflüssig wie ein Kropf".
>(Superfluous like a hunchback?)
>From what I've seen I'd say this: Bind an smtpd to the "submission" port,
>with proper smtpd_mumble_restrictions that conform to this standard.

How exactly is that done please?

Also, I would like to understand if this _separate_ smtpd that you are
speaking of will be able to share such things as the queue directory
with the smtpd that will be running on port 25. And will they both share
the same master?

Please educate me.

>I totally fail to see what ANOTHER port for submissions via SMTP is going to
>gain ANYBODY.

Well, just because you don't see any advantage, that doesn't mean that there
isn't any.

Obviously, _somebody_ thought that having a slightly _different_ kind of ESMTP
service (running on a different port) would be of some advantage, and that's
why we have an RFC (2476) which defines in some detail how the behavior of
the server running on this different port (587) should differ from that of
an ordinary (E)SMTP server running on port 25.

OK, so maybe at some level this stuff _is_ all superfluous. But that's not
what I was asking. What I asked was whether Postfix was known (or believed)
to fully support _every_ requirement of the relevant RFC (2476).

Has anyone ever checked this, e.g. by going through RFC 2476 line by line
and making _sure_ that Postfix either does conform, or else that it can
be configured in a way so as to fully conform?

That's mostly what I want to know.

Also however, I want to know, in detail, exactly how to configure it so
that it does indeed conform (to RFC 2476).

(It would be nice if there was a summry ``data sheet'' for Postfix, rather
like the data sheets that semiconductor manufacturers issue for the components
they sell... you know... something that says ``Conforms to RFC 821, 822,
xxx, yyy, 2821, 2822, ...'')

>Aha. ESMTP on port 587. How do these restrictions look like? Let's see
>4.1 General Submission Rejection Code

7. Interaction with SMTP Extensions

        1985 ETRN MUST NOT [ETRN]
        1846 521 MUST NOT [521REPLY]

OK, sure, I can figure out how to fully disable ETRN. No problem. But I
need to do that _only_ for the port 587 listener, and NOT for the port 25

How exactly do I do that?

Am I going to need two separate `master' processes and two separate

Note that I'm just picking out the ETRN thing as one example where the
behavior of the port 25 and 587 listeners should be different. There
appear to actually be _many_ ways in which the two should behave differently.
I want to know _exactly_ how to get Postfix running on _both_ ports 25 and
587 and with all required behavioral difference properly implemented for
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