MX record cannot be directly pointed to an IP
example.com. 14400 IN MX 0 10.10.2.55 is wrong.
Steps follows :
An A record must be difned for the IP 10.10.2.55 first.
test.example.com. 14400 IN A 10.10.2.55
After that we must point MX record to that IP
example.com. 14400 IN MX 30 test.example.com.