Usually it is acceptable for a lookup to fail because of a temporary failure of a system resource. When reading from a network database map (such as the DNS name server), temporary failures (such as server down) generally cause email to be requeued for a later try. However, you might sometimes find it desirable for a database map's temporary failures to be ignored. In such cases, you can enable this -t database switch. With it set, a temporary error will cause the mail to be delivered.

Note that failure of a key to be found in a database map is not a temporary error. Also note that this switch just determines the outcome of a message. It does not affect the nature of the returned value. To affect the return value on temporary failures, use the -T database switch (-T).