"Mark Smith" wrote:
> > -----Original Message-----
> > From: exim-users-bounces@???
> > [mailto:exim-users-bounces@exim.org] On Behalf Of Ian FREISLICH
> > Sent: 28 October 2005 09:10
> > To: exim-users@???
> > Subject: Re: [exim] Spam block idea:
> >
> >
> > Drop in the rcpt ACL would just 5xx that recipient, but
> > not the entire mail and the sending MTA (if it's an MTA) will
> > retry later with the good recipients.
> >
>
> That isn't the case. Drop immediately terminates the entire transaction,
> before the data ACL is even reached.
So lets examine the case:
recepients 'a', 'b', 'c' and "fake" 'd'.
HELO ...
220
MAIL FROM:...
250
RCPT TO:<a>
250
RCPT TO:<d>
550
Connection closed by foreign host.
Does the remote side give up on recipients 'b' and 'c' or does it establish
a new connection some time later and try them as well as 'a'?
RFC2821 (3.9) implies that it will retry:
SMTP clients that experience a connection close, reset, or
other communications failure due to circumstances not under
their control (in violation of the intent of this specification
but sometimes unavoidable) SHOULD, to maintain the robustness
of the mail system, treat the mail transaction as if a 451
response had been received and act accordingly.
Hence "remember that a fake address was a recipient and use deny
or drop in your pre-data ACL". That way you kill the whole mail,
not just one recipient.
Ian
--
Ian Freislich
