[Exim] Message Rate Limiting - Anti DoS ?

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Author: Jeremy Nicholls
Date:  
To: exim-users
Subject: [Exim] Message Rate Limiting - Anti DoS ?
Hi,

I've seen some comments in the archives regarding this, but has anybody got a
solution by which I can limit the number of individual emails per time period
from either a particular host or 'apparent' sender ?

Last night we suffered a type of DoS whereby a user of another ISP decided to
send >12,000 hate mails to one of our customers in under an hour. This
unfortunately didn't do our mail servers any good what with having to handle
NFS and LDAP queries as well !

So, has anybody come up with any way (assuming Exim doesn't already support
it) that will force a remote server to back off if it exceeds some threshold ?
I know that there are the smtp_accept_max* config options, but they're not
quite what I'm after.

Just for reference we're using 3.13 (and in places 3.20).

Thank,
Jerry.
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Supanet Ltd., Communications House,             Jeremy.Nicholls@???
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