Making users to use port 587 for submission emails

[Justin Zygmont]

On Sat, 10 Sep 2005, Sasa Stupar wrote:

>
>
> --On 10. september 2005 11:02 +0100 Paul Howarth <paul at city-fan.org> wrote:
>
>> On Sat, 2005-09-10 at 11:48 +0200, Sasa Stupar wrote:
>>> Hi!
>>> 
>>> I am running Sendmail 8.13.4 on FC4 with cyrus2. I have configured
>>> sendmail  to listen on ports 25 and 587. Since all of the client mail
>>> software use  port 25 by default instead of 587, how do I make users to
>>> use 587 and deny  access to 25? Something like: when they try to connect
>>> to port 25, they get  back error - you are not a server so you must use
>>> port 587.
>> 
>> Where are these users located?
>> 
>> You can turn off relaying for everywhere except localhost, which will
>> give any non-local clients a "relaying denied" error; using port 587
>> they will need to authenticate and that will override the relay check.
>> 
>> You can't easily tell the different between an MUA and an MTA connecting
>> to your port 25 - they are both acting as SMTP clients. This is why port
>> 25 blocking became necessary in the first place.
>> 
>> Paul.
>> --
>> Paul Howarth <paul at city-fan.org>
>
> Maybe this should be the next step in evolution of the mail servers - to 
> recognize MUA and MTA correctly. This is only my thinking.

SMTP could use a lot of redesign, I guess they never knew back then what 
they do now in terms of problems with spam, encryption, authentication, 
etc.  I'm suprised something hasn't been created to intend as a 
replacement, like ipv6 is to ipv4.