Making users to use port 587 for submission emails

[Sasa Stupar]

--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.

Regards,
Sasa