MX problem

[Craig Taylor]

Our organisation has multiple companies associated with it.  eg.
company1.com.au,  company2.com.au, company3.com.au.

The problem I'm having is we want to use internal DNS resolution (no
internet resolution required..incoming or ourgoing) but using only one
database file (eg. db.company1) for resolution.  Our HP-UX and AIX boxes
send system messages to people at user at company1.com.au as well as
user at company2.com.au and user at company3.com.au.  We have a server which will
resolve these email addresses however the problem I've got is for the Unix
boxes to resolve the MX records for company2 and company3.

If the resolv.conf is as follows:

domain company1.com.au

And named.boot as follows:

primary  company1.com.au  /etc/named.data/db.company1


What entry do I need to put into the db.company1 file for it to resolve an
MX query for company2.com.au and company3.com.au.  (Mail sent to
user at company1.com.au works fine).

Cheers
Craig Taylor