Re: asmtp 587 - quickie faq submission

From: Greg Panula (
Date: 09/10/02

Date: Tue, 10 Sep 2002 08:54:13 -0500
From: Greg Panula <>
To: freebsd-security@FreeBSD.ORG

Hmm, this original email/question is a good example why a mail-list might be a good thing.
Anyways, to help balance this thread away from noise and towards
signal... here is a quickie faq submission for this thread. :)

Q: What is ASMTP?
A: Authenicated SMTP, explained in RFC 2554

Q: What is ASMTP good for?
A: Allow the SMTP server to authenicate users before allowing them to
use the smtp service for sending mail. Useful if you have roaming users
that connect from foreign networks(e.g. hotel somewhere).

Q: How do I or my users make use of ASMTP?
A: The user's email client needs to be configured to authenicate
themselves to the smtp server. Earthlink has a FAQ section explaining
various email client configurations at

Q: Why does Sendmail listen on Port 587?
A: For compliance with RFC 2476 which states that seperating the
different parts of mail handling(submissions&transfers) is a good thing
and port 587 was deemed to be the port for handling submissions.
Sendmail 8.10.0 introduced DaemonPortOptions to support this. Checkout
for some quick info about DaemonPortOptions.

Q: How do I turn off the Message Submission Agent aka stop listening on
port 587?
A: Add FEATURE(`no_default_msa') your cf.m4 config file and recreate
your file.

Someone might want to verify the information above; I haven't done any
of it and stopped using&admin'ing sendmail a year or two ago. :)


Hans Zaunere wrote:
> --- Lyndon Nerenberg <> wrote:
> > >>>>> "Jose" == Jose Esteban Esquer Biskofski
> > <> writes:
> >
> > Jose> Hello, Ive been looking for information on what sendmail's
> > Jose> asmtp (port 587) is exactly, and how to close it. Ive had
> > no
> > Jose> luck, could someone please tell me how to get rid of it?
> > Jose> Thanks.
> >
> > Port 587 is the Mail Submission service (RFC 2476), and instead of
> > turning it off you should learn what it's for and then configure
> > your MUAs to use it.
> I disagree. I've been through docs/RFCs/etc and I have yet to see it's
> purpose. As far as I can tell, it's just sendmail listening on another
> port.
> The pertinent line in /etc/mail/
> 0 DaemonPortOptions=Port=587, Name=MSA, M=E
> and I've commented it out. If someone can tell me how I'm supposed to
> talk to it, I'd be interested - otherwise I see it just as an immature
> default. And, if it's setup for MUAs, why does it listen on all IPs?
> Just localhost, no?
> Thanks,
> Hans
> >
> > --lyndon
> >
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