On Thu, 2007-01-04 at 09:39 +0000, Philip Hazel wrote:
> 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.


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

some greylisting implementations don't whitelist at all or whitelist
(sender-IP, sender-addr, rcpt-addr) tuples, and as I pointed out, even
if it does whitelist, a periodic list cleaning can cause mail to bounce.

-- 
Kjetil T.



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