I am new to Roundcube and several users are asking me if there is a plug-in or add-on to Roundcube that allows users to create a white list and black list of email address or subject lines or other criteria?
Filtering should be done by the mail server, there is also a client side plugin http://sourceforge.net/projects/rcubefilters/ that may work.
we use sieve plugin that integrates with dovecot. Users can create filters on roundcube that are aplied on the server side