Given the command you posted (dig mydomain.com axfr), the error message (Transfer failed) is usually a "permission denied". Meaning, you should specify which systems are allowed to issue a "axfr" using the "allow-transfer" option in your named.conf file. Example from my DNS server.
Code:
// Define any "internal view" dns secondaries that can pull copies of
// zones. Use "none" if you only have one dns server.
acl "xfer-int" {
192.168.9.3;
};
...
// Load the internal mydomain.com zone
zone "mydomain.com" in {
type master; // Zone is a master
notify yes; // Send notifies?
allow-transfer { xfer-int; }; // Only allow transfers from secondaries
file "int/db.mydomain"; // Load zone file
};