Re: [Exim] MAIL ACL and sender verification

Hi Tabor, on Tue, 24 Dec 2002 14:13:58 -0500 you wrote:

> Actually the biggest one I've seen is that some MTAs treat 5xx at MAIL
> FROM as a temporary failure. Failing after RCPT is a lot more foolproof.

That could certainly be a problem (why oh why do people who are
intelligent enough to write an MTA not check the basic
functionality/standards conformance?). Although I can't say I've noticed
it on sendmail machines, but maybe that's not through looking hard enough,
or not getting a volume of mail such that it's a significant problem.

> 550-Verification failed for <blah@???>
> 550-Unrouteable address
> 550 Sender verify failed
> Seems pretty clear to me that it was the address used in MAIL FROM
> failed to verify and presumably the sender will recognize their own
> address in the error message.

Hopefully yes, and I agree that it's fairly clear (although I'm not sure
the particular choice of words couldn't be slightly better - I've modified
it slightly when I have used it myself), but I think a direct correlation
(via SMTP response) between the command that caused the error and the
error itself is a bonus. Again, like I said, I don't think it's critical
either way though, not least because IME 99% of failed verifications are
spam anyway. But it would be nice to at least have the freedom to
experiment with sender verification in the MAIL ACL, even if practically
speaking many people will choose to keep it to RCPT time.


Tim