[ On Tuesday, October 1, 2002 at 13:10:25 (-0700), Tom Marazita wrote: ]
> Subject: Re: [Exim] Wish list (I think) regarding sender verify callout.
>
> Philip Hazel wrote:
> >
> > The whole point of callout is to check that the host will accept a
> > bounce from you before you accept the message. If you aren't going to
> > enforce that, there's no point in doing the callout at all.
>
> I agree; however, it seems the bounce can fail for two (maybe more) reasons:
>
> 1) The RCPT TO: can fail, in which case I'm happy to reject
> the message since it means the sender was invalid. I see a large
> number of these situations in the log files, and they are sender addresses
> that have usually been forged and for which I do not want to accept the mail.
>
> 2) The MAIL FROM:<> can itself fail, which indicates the host at the
> other end has a poorly configured mailer; or at least
> that's what it seems to have indicated with the hosts I've
> come up against recently. The sender might still
> actually be valid though, and in that case I might still want
> to accept the message even if I can't verify it due to their not
> accepting the bounce.
There's also the case where the host doing the callout is misconfigured
(or its DNS is misconfigured) and encounters errors sending its own
greeting command, or even the host doing the callout is on a DNSBL or
other blacklist used by the host handling the sender address. The
callout MUST NOT "fail" in those cases. If the bounce ends up in the
postmaster mailbox as a result then that's a "Good Thing(tm)"!
--
Greg A. Woods
+1 416 218-0098; <g.a.woods@???>; <woods@???>
Planix, Inc. <woods@???>; VE3TCP; Secrets of the Weird <woods@???>
