Re: [exim] rDNS lookup problem

On Fri, Jun 10, 2016 at 08:56:07AM +0100, a.smith@??? wrote:
> For example when sending from 93.191.32.251 I see:
> X-Host-Lookup-Failed: Reverse DNS lookup failed for 93.191.32.251 (failed)

There are three different DNS rcodes that may be referenced as "failure",
they correspond to different situations.

> Any clues as to why Exim is failing when nslookup/dig from the same
> host using the same DNS server work?

Due to resolver timeout (packet loss in network) or "ServFail" DNS rcode,
which is a temporary error (client should wait and retry later).
--
Eugene Berdnikov