Re: [Exim] callout suggestion

On Mon, 2004-02-23 at 11:09 +0000, Philip Hazel wrote:
> On Sun, 22 Feb 2004, Wakko Warner wrote:
>
> > What about using the same MAIL FROM as the RCPT TO when doing the call out?
> > If it causes loops, it isn't on your end =)
>
> It's probably worth repeating my view on this: What Exim is trying to
> achieve is to get an answer to the question "Is it likely that an
> attempt to deliver a bounce message to this address will succeed?" Since
> Exim sends its bounce messages with sender "<>", that is what it uses
> for sender verify callouts.

For sender verification callouts you are 100% correct.

For _recipient_ verification callouts I think Exim's current behaviour
is suboptimal.

If, for example, I do recipient verification callouts for mail from
+relay_hosts, I'm going to refuse to allow my relay_hosts to relay mail
to the Exim list, because the Exim list doesn't accept MAIL FROM:<>, and
with good reason. There are plenty of other addresses which only
_receive_ but never send email, which will quite reasonable reject MAIL
FROM:<> at RCPT time.

I suggest that _recipient_ verification callouts should optionally be
permitted to use a 'real' address, perhaps the MAIL FROM: address in the
transaction being verified, because otherwise recipient verification is
just increasingly broken.

--
dwmw2