MX TTL syntax

hi,


i want to keep the records of two domains syncronous.
For this reason i configured the same zone data file
for both domains in the named.conf.

example

zone "doamina.mydomain.do" {
type master;
file "zone-file";
};


zone "doaminb.mydomain.do" {
type master;
file "zone-file";
};


in the zone file i keept the left sides
non fully qualified, so that the records are made fully
qualified by adding the ORIGIN.

Works so far, i only have problems with the MX Records.

Obviously this does not work, because a mx querey for
domainb.mydomain.do cannot be answered.

domaina.mydomain.do 3600 IN A 10 mailserver.domainc.do

can someone tell me about the correct syntax, specifieing
a mx record for a whole domain without having to specify
the domain fully qualified and also adding a ttl to that record.

of course i could write

domaina.mydomain.do 3600 IN A 10 mailserver.domainc.do
domainb.mydomain.do 3600 IN A 10 mailserver.domainc.do

in the same file, but this would be redundant.

many thanks
--
Timo