Firstly we recommend you check to see what addresses are counting against your SpanTitan license. SpamTitan comprehensive reporting module allows you full visibility on license usage. On v5.11 of SpamTitan and later, you can run a ‘License Usage Report’ via the Reporting > Reports tab.
If you see invalid addresses counting against your license, you should ensure you have recipient verification (RV) enabled. In SpamTitan, RV is configured for *each* domain under System Setup -> Mail Relay (Domains) tab. Dynamic, LDAP and List are the available RV methods. We recommend using Dynamic Verification.
If using Dynamic RV, you will need to enable this on both SpamTitan and your mail server. Below are some links on how to configure various Exchange servers.
How to configure Exchange 2007.
How to configure 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.
If all addresses are valid, you may need to consider increasing your licensing band and the SpamTitan licensing department can advise you on the cost of this – email us.