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

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

> > >       * 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,


[snip]

> the retry entry for B will be for the host if it sends 4xx in the
> banner, right?


True, but nevertheless, I still don't think it will behave as you
suggested. At a host level, Exim will believe that host A is ok, but
host B is permanently dead. So it will stop trying host B. But that
won't make it bounce the recipient until it (the recipient) times out.

At least, that's what is supposed to happen. There are always bugs...

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