Author: Adam D. Barratt Date: To: exim-users Subject: Re: [exim] HostEurope anybody
On Sat, 2018-02-17 at 15:15 +0000, tech-lists via Exim-users wrote: > An IP *cannot* resolve to a CNAME as per RFC 1034. It must resolve to
> an A-record, hence the error "reverse dns failure".
Nope, I think you're wrong here. The nearest suggestion that I can find
in 1034 (although not quite on the correct topic) is:
<quote>
Domain names in RRs which point at another name should always point at
the primary name and not the alias.
...
Of course, by the robustness
principle, domain software should not fail when presented with CNAME
chains or loops; CNAME chains should be followed and CNAME loops
signalled as an error.
</quote>
There's absolutely no "must" in there, and indeed a "should not fail".
Indeed, the concept of RDNS delegation, as per e.g. RFC 2317 (which is
what the original query appears to revolve around) *requires* the
immediate target of a reverse lookup to be able to be a CNAME.
