The Advanced Security for Outlook

from http://www.mapilab.com/outlook/security/ is free Outlook add-in that allows end-user to take control over Outlook security alerts.

It allows end-user to determine the violator as well as specifying the status for this program for future occasions e.g. allow access, block access or run the default Outlook handler. Future specified actions will be executed automatically and Outlook Security will cease to annoy you with messages concerning attempts to access e-mail addresses you have stored in Outlook.