Hi Phil.
Am Sonntag, 20. Mai 2007 21:51:04 schrieb Phil Pennock:
> On 2007-05-19 at 15:34 +0200, Peter Thomassen wrote:
> > $ host -t mx mail.peter-thomassen.de
> > mail.peter-thomassen.de MX 10 mail.a4a.de
> > mail.peter-thomassen.de MX 20 rescue.a4a.de
> > $ host -t mx mail.glv.at
> > mail.glv.at CNAME glv.at
> > glv.at MX 10 mail.a4a.de
> > glv.at MX 20 rescue.a4a.de
> > $
>
> This, unfortunately, is broken. The hostname provided by MX resolution
> is not permitted to be a CNAME record; it may work for some combinations
> but other clients won't support it, so you'll not be reachable by some
> people (those following the standards carefully).
>
> Another useful and readable RFC which is relevant here is:
> RFC 1912 Common DNS Operational and Configuration Errors
> and section 2.4 of that covers CNAME usage, including covering the issue
> with MX records, providing pointers to the relevant standards-track RFC
> comments on the issue.
In RFC 1912, I can only find that MX records themselves shall not point to
CNAME type hostnames. However, I cannot find that the host whose MX server we
are looking for may not be a CNAME alias. The hostname provided by MX
resolution is mail.a4a.de (rescue.a4a.de) which is not of type CNAME.
I have read section 2.4 several times now. If I got it wrong nonetheless,
please give me a quote :-) Maybe, mail.glv.at was a bad example, and we
should rather investigate sub.glv.at:
$ hostx -t mx sub.glv.at
sub.glv.at CNAME glv.at
glv.at MX 20 rescue.a4a.de
glv.at MX 10 mail.a4a.de
$
Have a nice day.
--
Peter Thomassen • Steigerwaldstr. 4 • 97076 Würzburg • Germany
http://www.peter-thomassen.de/ • mail@???
fon +49-931-2705351 • mobil +49-176-63159879
