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Re: Why do so few mail providers support Port 587?

  • From: Owen DeLong
  • Date: Wed Feb 16 04:43:53 2005

--On Tuesday, February 15, 2005 21:30 -0500 Sean Donelan <[email protected]> wrote:

On Wed, 16 Feb 2005, Thor Lancelot Simon wrote:
This is utterly silly.  Running another full-access copy of the MTA
on a different port than 25 achieves precisely nothing -- and this
"support" has always been included in sendmail, with a 1-line change
either to the source code (long ago) or the default configuration or
simply by running sendmail from inetd.

What benefit, exactly, do you see to allowing unauthenticated mail
submission on a different port than the default SMTP port?

Similarly, what harm, exactly, do you see to allowing authenticated
mail submission on port 25?
How do you tell the difference.  Yes, you can run any protocol on any
port.  But Well-known ports have a better chance of working across today's
Internet full of NAT and firewalls.  By keeping authenticated and
unauthenticated protocols on different ports, its easier to control
the use of unauthenticated protocols at various middle-points in the
network without affecting people using authenticated protocols.

Port 25 accepts unauthenticated e-mail for various legacy reasons, which
are not going to go away soon.

Port 587 is supposed to be authenticated, although some programmers and
system administrators think its too hard to ask for authentication.

I would argue that in today's environment, a well implemented mailserver
supports authenticated submission on ports 25 and 587, and, unauthenticated
delivery on port 25.  It may also support some level of unauthenticated
submission by local users on port 25, if necessary.

If you accept unauthenticated mail on Port 587, don't complain about
the spam you are going to get.

If you accept unauthenticated mail on port 587, the problem isn't the
spam you will receive, it is the spam you will forward.


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