[exim] Pre-emptive fallback hosts ?

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Author: Jerry Nicholls
Date:  
To: exim-users
Subject: [exim] Pre-emptive fallback hosts ?
Good Day All,

Before I attempt to cook up a home brew version of this, I was wondering
if any one else had done anything similar.

I have just begun to look at the suitability of using fallback hosts to
improve the overall throughput wrt our smarthosts. What I was also
pondering on was using the fallback hosts to ameliorate the problems
with blacklisting due to excessive spam sent to the likes of AOL and
Yahoo. We take a hard line on our customers either sending spam, or
having open relays, but unfortunately we usually only see the issue when
the receiving server blocks us and our queues rise.

I'm looking to put together a configuration akin to grey listing whereby
if too many emails from a customer fail or defer then all mail from that
IP address is automatically shunted onto the fallback hosts without even
trying. Then at some later stage (timeout) that customer's email will
again be tried first by the smarthost. Hopefully this way only our
fallback hosts will be temporarily blocked whilst legitimate email will
get through on the smarthosts.

Has anyone else tried this, or is it a completely daft idea ?

Thanks,
Jerry.
-- 
Jerry Nicholls                       E: Jerry.Nicholls@???
Core Internet Systems Designer       W:            http://www.zen.co.uk/
Zen Internet                         T:                    0845 058 9000
                                     F:                    0845 058 9005