Re: RFC 2?821 and CNAMEs

[Ian Jackson <ian@davenant.greenend.org.uk>]

martin f krafft writes ("Re: RFC 2?821 and CNAMEs"):
> Of course I can ensure that, and that's what I had a while ago: for
> each of my road-warriors (rw.madduck.net; 19 of them; no, not all
> laptops; long story), I had a separate pair of MX RRs.
> 
> I sought to simplify that and created rw.madduck.net with two MX RRs
> and CNAMEd the 19 domain names to that,

You should definitely change this, not just because my strict reading
of the state of the standards forbids it, but also because the
behaviour of other MTAs is not always what you want.

In particular, I have seen MTAs which would (taking your situation as
a concrete example, and when relaying mail eg as a smarthost), after
receiving a mail with
   RCPT TO:<whatever@lapse.madduck.net>
would look lapse.madduck.net in the DNS, see it's an alias, and then
decide that the right thing to do was to send to your MX
   RCPT TO:<whatever@rw.madduck.net>

(Obviously this behaviour is completely barking.)

Ian.