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

  • From: Joe Maimon
  • Date: Fri Feb 25 11:37:31 2005

[email protected] wrote:

[email protected] wrote:

On Thu, Feb 24, 2005 at 04:02:20PM -0700, Smoot Carl-Mitchell wrote:

On Thu, 2005-02-24 at 17:14 -0500, Jim Popovitch wrote:

If supporting one port is y hours of time and headache, then two
ports is closer to y*2 than y (some might argue y-squared). 587 has
some validity for providers of roaming services, but who else? Why
not implement 587 behavior (auth from the outside coming in, and
accept all where destin == this system) on 25 and leave

the rest alone?

I did run into a case where supporting port 587 was useful. I found
out the hard way that one Internet service provider for hotels
blocked outbound port 25, but not 587. So sending outbound mail to
my mail relay would have been impossible without support for port
It's so funny. On this list many argued Port 25 outgoing must
be blocked only to notice, that users actually seem to need
it to send mail. Now we must configure our mailservers to
listen on 587 to circumvent these filters, that were stupid
in the first place.

Now to my prophecy mode: Spammers will start using 587 to
spam, which we then also all block outgoing, notice again
that customers still want to send mail and open another port
... 652 maybe. But this in a "while (true)" loop until we run
out of ports.

That's being a bit disingenuous. The discussion here hasn't been to
open up port 587 to relay for all comers, but rather to open it up for
authenticated use only. If spammers start using it, then it's a result
of either poor authentication security or an understaffed abuse
department. I'll agree with you on one thing, though -- the whole
business of port 587 is a bit silly overall...why can't the same
authentication schemes being bandied about for 587 be applied to 25,
thus negating the need for another port just for mail injection?


In this while loop the break is that when authenticated customers abuse the authenticated service they will be terminated, not the service.

I do not see a repeat step here.

Oh you mean un-authenticated direct-to-mx spammable 587? Yes please, keep that turned off.

We need 587 because trusted authentication in SMTP does not transit with the message. So there is no way to require authenticated email only from all systems that would be worth a damn. Therefore, the goal is to corall the message submitting users onto authentication required gateways into the smtp network and reserve the ability to only allow port 25 to known servers.