As you have probably already read on assp documentation the "assp email inteface" is a powerful assp feature which permits to add or remove email to the Whitelist, report spam, or false-positives improving the bayesian filter.
For example the "REPORT" button that you can see on the "assp deluxe for cpanel" log pages uses the assp email interface to report false positives. ASSP email interface (assp-spam@yourdomain.com assp-white@yourdomain.com and so on) accepts reports only if the sender client uses smtp auth on (only from smtp authenticated users).
Horde and Squirrel mail are automatically configured by assp deluxe for cpanel to use the assp email interface.
