Ian FREISLICH wrote:
"Mark Smith" wrote:
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ian FREISLICH
Sent: 28 October 2005 09:10
To: [email protected]
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
Interesting thread. Might I ask, what is the likely effect (if any)
when one's Exim is configured to neither advertise nor accept 'pipelining'?
Bill Hacker
--
## List details at http://www.exim.org/mailman/listinfo/exim-users
## Exim details at http://www.exim.org/
## Please use the Wiki with this list - http://www.exim.org/eximwiki/
