Re: [exim] RBL Blocking

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Author: Viktor Dukhovni
Date:  
To: exim-users
Subject: Re: [exim] RBL Blocking
On Sat, Feb 22, 2014 at 10:02:07PM +0100, Heiko Schlittermann wrote:

> And I'm not sure, but I think, you should not block messages to
> postmaster. To achieve that, you have to wait for RCPT.


One should generally accept most mail to postmaster and abuse.
That way complaints about false positives can be handled.
Unfortunately, many postmaster/abuse mailboxes are subject to
content-based quarantine, but provided FP complaints don't match
content filter rules they should get through.

> Rejecting with 5xx at SMTP connect is about the same as a TCP
> reject, as Viktor says, most MTA will retry later or at your fall
> back MX.


Though many RBLs are very good, and the FP rate is quite low, there
will be FPs from time to time. When these happen, it is useful
for the legitimate sender to receive a bounce promptly. So rejecting
in a manner that causes legitimate MTAs to queue and retry is
unwise.

> (But spam senders won't care, so probably it helps. Remains the
> postmaster issue as a reason to wait for the RCPT.)


Yes, and useful logs.

-- 
    Viktor.