MX records fully qualified?

[Larson, Matt]

> Is it true that hosts in MX records must be fully qualified?
> myinternet.com complains if you try to set a mx
> host like 'ntrack.com') that the host in the MX record must be fully
> qualified (i.e. mail.ntrack.com instead of ntrack.com).
> I don't seem to be able to create a fully qualified host name 
> to use as a mail server.

There's a terminology problem here.  A fully qualified domain name is an
absolute, unambiguous reference to a node in the name space, i.e., it
includes every label name up to and including the root's null label.  In
other words, a fully qualified domain name ends in a dot.

So both ntrack.com. and mail.ntrack.com. are fully qualified domain names.
You can put any domain name you like on the right side of an MX record,
provided that that domain name has an A record associated with it.  Looks
like this user interface is being unnecessarily restrictive.  (Although if
there's no A record for ntrack.com, then prohibiting you from using it on
the right side of an MX record is reasonable.)

> I'm using Public DNS (soa.granitecanyon.com) and if I
> try to create mail.ntrack.com the script complains that both
> mail.ntrack.com and ntrack.com are using the same IP.

That's just wrong on their part.  There's no prohibition on multiple domain
names having A records with the same RDATA.

> Also the script seems to suggest that an MX record host can't be a CNAME.

That's correct.

Matt
--
Matt Larson <mlarson at netsol.com>
DNS Platform Manager
Network Solutions Registry / www.nsiregistry.com