Re: [exim] Extremely Simple(?) greylisting with exim?

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Author: Philip Hazel
Date:  
To: Kjetil Torgrim Homme
CC: exim users, Chad Leigh
Subject: Re: [exim] Extremely Simple(?) greylisting with exim?
On Thu, 4 Jan 2007, Kjetil Torgrim Homme wrote:

> here's the scenario:
>
>       * server sends message to A (highest MX priority), and is defered
>         due to greylisting.
>       * server now tries to send message to B (lowest MX priority) which
>         always defers.
>       * server notes that B defers in retry database
>       * some time later, it retries A, and it is successful.

>
> repeat this for some time. eventually you get this:
>
>       * server sends message to A, and is deferred due to greylisting.
>       * server tries B, which defers.  it looks in retry database, sees
>         that B hasn't worked for a long time, and BOUNCES THE MESSAGE
>         IMMEDIATELY.


That isn't right.

It is *recipients* that are deferred by greylisting, not messages. When
a recipient is deferred, Exim notes that the recipient, not the host,
has had a temporary error. (In the latest releases it is the
sender+recipient combination, not just the recipient.) So, the above
scenario will happen only if A defers *the same recipient* due to
greylisting on the second occasion, and as I understand it, this
shouldn't happen because the recipient was previously accepted.

-- 
Philip Hazel            University of Cambridge Computing Service
Get the Exim 4 book:    http://www.uit.co.uk/exim-book