Re: [exim] greylisting issue

On 4/20/2005 10:20, "Craig Jackson" <cjackson@???> wrote:

> Hi,
>
> I am using Exim 4.50 and greylisting for an email gateway. I receive an
> email not in the database; Exim sends the 451; and the vast majority of
> mail servers resend. It's the few mail servers that I need to receive
> mail from that don't resend that I'm concerned about. For example,
> Southwest Airlines does not always resend. This is a big problem. I'm
> wondering what people on this list who use greylisting do about this.
> Would it be better to send 450, for example? I've tried whitelisting,
> but that's ex post and thus kind of useless.

You do need to provide for whitelisting. Aside from outright failures, some
senders do odd things with the 4xx error code. Yahoo! Groups does (or did
when we started greylisting) switch the address to getting group messages
via the web only, upon the first 471 error code.

There is really no point in greylisting either large senders who behave
properly, neighbor senders who behave properly (even if they are small in
the world at large), folks like Ticketmaster where the would-be recipient
expects the message *now*) and known senders who mess up but whose mail you
(your customers) want. (Ticketmaster seems to be in the "mess up" group, in
that retries come from various servers in the outgoing farm.)

We bypass greylisting for "trusted" (per our database) sending machines
where SPF is right for the message. (We don't reject anything on SPF; we do
do things like the above with it, and we do add Spamassassin [smallish]
points for SPF failures.)

--John