Topic Last Modified: 2007-05-08

If you select this option, the Simple Mail Transfer Protocol (SMTP) service will try to verify that the client's IP address matches the host/domain submitted by the client in the EHLO/HELO command. If the reverse DNS lookup is successful, the RECEIVED header remains intact. If the verification is unsuccessful, unverified appears after the IP address in the RECEIVED header of the message. If the reverse DNS lookup fails, RDNS failed appears in the RECEIVED header of the message.

Because this feature verifies addresses for all incoming messages, its use could affect SMTP service performance. Clear the check box to disable the feature.


To enable reverse DNS lookup

  1. In Microsoft Management Console, select the SMTP virtual server, and then click Properties on the Action menu.

  2. On the Delivery tab, click Advanced to open the Advanced Delivery dialog box.

  3. Select the Perform reverse DNS lookup on incoming messages check box.