Error message
========================
Message 1HVHR1-0000Rh-5m is not frozen
LOG: MAIN
cwd=/usr/local/cpanel/whostmgr/docroot 4 args: /usr/sbin/exim -v -M 1HVHR1-0000Rh-5m
delivering 1HVHR1-0000Rh-5m
LOG: MAIN
== postmaster@netspace.net.au R=lookuphost defer (-1): host lookup did not complete
========================

ssh to server as root and run:
dig netspace.net.au mx

If you get a response, then the server should get a response as well If you don't get a response, run:
cp /etc/resolv.conf /etc/resolv.conf-ori1
nano /etc/resolv.conf

check nameserver IP.
==================
nameserver 123.123.123.123
search nt-340.nocser.net
==================
make sure nt-340.nocser.net resolve to server IP. If iit resolved. then run:
dig @123.123.123.123 netspace.net.au

If no respond make sure the IP is correct. Can check with Datacenter.