MX records definition

[Kevin Darcy]

Igmar Palsenberg wrote:

> On Fri, 15 Dec 2000, Paul Bijnens wrote:
>
> >
> >
> > We have a problem with sending mail to one specific site
> > ("cannot check MX records for recipient host").
> > Because they do receive mail from other people now and then
> > they believe it has something to do with us.
> > However, I believe it is something in their DNS setup with
> > their MX record.  But I'm no expert.
> >
> > What I find strange is that when I dig for the mx record,
> > there is no "additional section" with A records for the hosts.

Well, technically, Additional Section records are not mandatory except in
the special case of glue records. Your (Paul's) mail software *should* be
smart enough to get those A records via subsequent queries even if they are
missing from the Additional Section of the MX query response.

> >   $ dig writetc.com mx
> >
> >   ; <<>> DiG 8.2 <<>> writetc.com mx
> >   ;; res options: init recurs defnam dnsrch
> >   ;; got answer:
> >   ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4
> >   ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0
> >   ;; QUERY SECTION:
> >   ;;  writetc.com, type = MX, class = IN
> >
> >   ;; ANSWER SECTION:
> >   writetc.com.                23h59m27s IN MX  0 mail.writetc.com.
>                                                 ^^^^
>
>                                         Sounds pretty bogus to me.
>
> Looks like the 0 in the MX record priority is giving problems.

There's nothing wrong with an MX preference value of 0. I use it all the
time.

Using aliases as  MX targets, though, is highly illegal, as you
(Igmar) pointed out...


- Kevin