Maia Mailguard is a Spamassasin front end that uses its own version of Amavisd to scan and process incoming and outgoing emails. I have tried looking for other frontends, but they do not seem to be able to match Maia, when it comes to the ease of use for end users. It is not the easiest frontend to install, but it is worth the trouble because of the end user response that I have had from it so far. Spamassassin and the RBL block lists do a good job of stopping most of the spam getting in, but end user participation is still good, for when the spammers switch their techniques. There are other anti spam technologies that I could use, along with Maia, but I will usually add them if the client feels that Maia and the RBLs are not good enough.