Dynamic Recipient Verification (DRV) is the easiest form of Recipient Verification to use and manage. To use DRV it is required that your mail server rejects mail addressed to invalid addresses (Recipient Filtering). SpamTitan can then use your mail server to verify if a recipient specified on an incoming mail is valid or not. See What is Recipient Verification?
See the links below for information on enabling Recipient Filtering on commonly used mail server software:
Recipient Filtering for Exchange 2010
If you are using a default standalone (no Edge Transport Server) installation of 2010, the Anti-Spam functionality is not installed. Therefore, you need to follow this article:
Once Recipient Filtering is enabled log on to the SpamTitan web interface. Browse to System Setup > Mail Relay > Domains. Edit a domain and select "Dynamic Verification" and enter your mail server IP as the Verification Server.
This will allow SpamTitan to verify the recipient addresses of all incoming mail. Any mail addresses to invalid addresses will be dropped. This will aid the spam block rate and keep your daily license usage count accurate.