Sorry to be replying late... But, if anyone is interested, we have a squirrelmail plugin and a small C program to handle turning spam-filtering on/off and also for setting vacations and forwards from within SquirrelMail. It does not require running your webserver as the vpopmail user. Combined with the "sasql" plugin, it gives users the ability to set many vpopmail options without having to ever look at qmailadmin.
Let me know if anyone has interest in this. The only thing I ask is that if you find it useful, that you contribute any cleanup back to me. Thanks, Charles