If your users are using either Mozilla Thunderbird or Microsoft Outlook, you should look into my plugin: SpamAssassin Coach. This plug-in/extension basically automates the task of sending a TELL command to a local or remote spamd server via the spamd protocol to report/revoke spam or ham messages. All users have to do is select a spam message in their inbox and hit Learn As Spam and the message will be reported to a specified spamd server.
NOTE: This plugin is still under development and undergoing testing. I will be releasing a new version for Mozilla Thunderbird soon that should be working well. The Microsoft Outlook version (which seems to have some problems) will need to be completely rewritten in Visual Basic, but stay tuned for that update as well. SpamAssassin Coach - https://sourceforge.net/projects/soc2006spamd/
