virtual domains and zone files

[Andrew]

My mail server hosts a virtual domain that does not include any hosts in 
it. Here is the zone file I use with this domain.

# cat /etc/namedb/master/arda.homelinux.net.zone
$ORIGIN .
$TTL 10800      ; 3 hours
arda.homelinux.net      IN SOA  europa.arda.homeunix.net. 
postmaster.arda.homeunix.net. (
                                 20030416   ; serial
                                 10800      ; refresh (3 hours)
                                 3600       ; retry (1 hour)
                                 604800     ; expire (1 week)
                                 3600       ; minimum (1 hour)
                                 )
                         NS      io.arda.homeunix.net.
                         NS      europa.arda.homeunix.net.
                         MX      10 callisto.arda.homeunix.net.

As things stand now, I can deliver mail to user at arda.homelinux.net but I 
would like to know if this zone file looks reasonable or if there are 
elements that don't need to be there.

Andrew