Re: [Exim] SMTP

>From: Tony Finch <dot@???>
>To: "Alan J. Flavell" <a.flavell@???>
>cc: "Exim-Users (E-mail)" <exim-users@???>
>Subject: Re: [Exim] SMTP
>Date: Wed, 30 Jun 2004 16:09:28 +0100

...

>> Some folks will tell you that mail submission protocol is a
>> preferable solution to this requirement than authenticated SMTP.
>> Maybe we should look at that too.
>
>Definitely. It makes message submission much more reliable,
>and it allows users to have a single configuration that works
>anywhere. You will need to support both tls-on-connect on port 465
>as well as standard submission on port 587 in order to support all
>the clients out there.

Rescorla[1], page 358, says:

RFC 2487 was published roughly at the same time as the TLS
specification, RFC2246. Although SMTP over SSL had been in
use for some time, RFC 2487 codified the rules for its use. A
separate ports strategy (SMTPS) was briefly in use but dod not see
the wide deployment and has been obsoleted by STARTTS.

So it really necessary to handle tls-on-connect on port 465 (SMTPS) ?
Are there clients out there than have to use this rather than STARTTLS
on port 25 or port 587 ?

[1] "SSL and TLS", Eric Rescorla, Addison-Wesley, 2001, 0-201-61598-3