Identifying DNS Problems

DNS problems tend to originate from several sources:

Broken network connectivity - a host cannot access the DNS server and thus its DNS queries time out.

Missconfiguration - the DNS server contains wrong or partial data. For example, it knows a given domain, but not who handles mail for that domain.

De-synchronization - the master DNS server was updated, but its secondaries have not pulled the info yet, or some other server still caches its old data. This will cause transient failures that will disappear after the original data's TTL (Time To Live).