Disappearing MX record for DNS BIND

Do you manage your primary DNS server? Try to make some changes to change "serial number" to propagate these updates to Internet. When you use NSLOOKUP, try to connect to different DNS servers and check if your domain has this record. May be it's not completely propagated through? Do your clients report any problems sending e-mails to you? Generally, try to identify problem (if it exists at all) and isolate it - is it your local DNS server's problem, or Internet connectivity/propagation problem.

Good luck.

This symptom comes when two different DNS servers have two different answers for the zone. This can happen when one of the two has failed to transfer the zone. It can also happen when the zone file is changed but the serial number was not. The primary will pick up the change if it is restarted, but secondaries will not pick it up.

Steps: determine which servers are being used. query each name server listed by the root servers as well as each name server listed in the SOA.

"whois tanj.com" will show the name servers listed with the name servers. One of those is it2.tanj.com

"nslookup -q=SOA tanj.com it2.tanj.com" will give you the name servers that it2.tanj.com lists as authoritative.

You can then check each of those servers for the SOA for the zone "tanj.com". Confirm the serial number from each name server matches.

Other things that will stop the zone from propagating to the secondaries:
a)A "transfer" restriction in the named config file.
b) Port 53 (TCP) may be blocked at a firewall.
c) the secondary may not be set up to host the zone.