Hi guys, I really do appreciate all the help.
Ok so I installed BIND9 and started working through the Split-DNS doc.
Unfortunately there is no /etc/named.conf file, there is a /etc/bind9/named.conf - (apparently I am to make any changes in the named.conf.local file - which does not contain any of the text listed in the split-DNS doc)
I did find the forwarders entry in named.conf.options and I added all of the DNS servers we have in there.
I eventually worked out the files and made the changes as I thought they should be.
Put the mail.doamin1.com zone into the named.conf.local file.
Put the Forwarders into the named.conf.options file
Created a db.mail.domain1.com file
Changed the resolv.conf to have the local ip in there
I did an nslookup mail.domain1.com on the mail server and it returned
** server can't find mail.domain1.com: SERVFAIL
I enabled the query-source address * port 53 in the named.conf.options file - not sure if I should have done this. I will disable and test it.
Also in the resolv.conf I just added the local ip addr to the file, should I have done anything else with it.
Thanks for your help guys