Re: [exim] Munged envelope sender addresses in normal mail f…

On Thu, 2006-07-27 at 21:32 +0200, Magnus Holmgren wrote:
> Speaking of BATV and similar sender rewriting - many kinds of mail-based
> server software use the envelope sender address to identify the sending user.
> For instance, if I'm going to enable import of mail in Bugzilla, the sender
> should be required to have an account or the mail will be rejected (it helps
> in case some spam slips through, but if you feel lucky it's of course
> possible to create an account for anonymous posts).
>
> The From: field may be the best place to look after all, but as always, it's
> not possible to accept some recipients and reject some after DATA. When
> rejecting at RCPT it's also easier to tell the sender what went wrong, I
> think.

I don't think it matters much in practice. e.g. Outlook reports errors
from RCPT TO very badly so DATA is preferred, but that's a moot point
since it won't be delivering directly to the Bugzilla MX.

> So, which one is better?
>
> 1. Look at the From: field and reject the whole message if the address is not
> recognized?

in this specific case (bug trackers), it is unlikely there will be other
recipients, so it's not a big problem. to reduce the probability
further, set up a separate IP address for the installation. Sendmail
will try to optimise deliveries so that RCPT TO are aggregated across
domains if they share MX (I don't think Exim does this), so
holmgren@??? (assuming you're on Cc) and
32342@??? will be just one delivery as both domains
point to mail.lysator.liu.se.

however, the "standard" way of handling this is to accept the first RCPT
TO, and defer any subsequent RCPT TO. this way you force the sending
MTA to deliver multiple times, and the DATA response can be
individualised.

it may be a feature that it's rejected all or nothing, though. I guess
we've all seen messages with "I apologise to everyone receiving two
copies, I made a typo in the address list in my first attempt".
--
Kjetil T.