FYI, ClamAV has been removed from Dotdeb, since it is more actively maintained on Debian Volatile.
Volatile is now part of the Debian project and will be activated by default on Debian Lenny. Its goal is to provide up-to-date packages of some specific pieces of software (ClamAV, Spamassassin for example). Please use it instead of Dotdeb for your mail-filtering packages.