RE: [Exim] Rejecting due to reverse DNS lookup failture

> Whilst I worked for an ISP we had the same issue. I implemented the DNS
> lookups during an upgrade. Marketing went nuts about this because we got so
> many complaints. The standard arguments failed to cut it. When we did some
> analysis of the logs, we found that 1 in 5 unique IP addresses were failing
> the lookups. So we had to abandon the check.

I suggest to add an X- header to point out the problem, like you can do with
RBLs. I just don't know how to do that off hand.

The funniest complaints about open customer relays are sent from companies
where the header shows that they operate an open relay, too.

Michael