Re: [exim] exim 4.4 authentication

On Mon, Mar 14, 2005 at 10:43:00AM +0000, Alan J. Flavell wrote:
> There is still one problematic area with that, however. When users
> contrive to produce a mail which the server rejects (e.g they try to
> send a mail with its envelope-sender set to a defective address, or
> with broken header syntax etc.) then it seems some clients get very
> confused by the 5xx response from the server. In some cases, the user
> goes away believing their mail has been sent successfully, when in
> fact it has not. In other cases, the client host appears to treat the
> 5xx as a temporary failure, and keeps retrying the mail at 10-minute
> intervals for days on end, until we spot the problem.
>
> Would there be any improvement in this area if we were to move to
> using the client submission port(s) instead of the SMTP port 25 ?

That's the difference between MTAs and MUAs. An MTA will (should)
understand the 5xx and 4xx responses correctly, and so they can be used.
An MUA will not necessarily understand them.

Therefore, mail sent to the submission port should never be rejected
immediately, but should be accepted and bounced. (Of course, it's the
opposite with port 25).

SMTP and mail submission are really two different things that should
never have been merged in the first place, IMHO. :-(

Matthew


--
Matthew Newton <mcn4@???>

UNIX and e-mail Systems Administrator, Network Support Section,
Computer Centre, University of Leicester,
Leicester LE1 7RH, United Kingdom