Following redshift82r's instructions posted elsewhere in the forums, I loaded Roundcube on our MLS and added the managesieve plug in. Once everything was working, I was able to setup a rule to move messages with the string ***JUNK MAIL*** in the subject to the junk folder. This seems pretty effective at keeping the inboxes clean, while allowing end users to check their own junk folders so long as they are using IMAP.
I'm real green still, so I'm looking at the following (over the next several months):
1) Default templates for Roundcube mailboxes (default folders) and default manageseve filters
2) Updating whitelists/blacklists with some script (maybe called from cronjob) to allow users to put false positives in one folder and spam in another to train spamassassin <-- this might turn out to be a pipe dream
3) More customization in spamassasin rules to automaticaly delete/bounce spam with certain characteristics
So far, so good, though. Got a snapin running that allows carddav sync with MLS address books. Looking at getting calendar snapin to work as well.
I am getting e-mails from spamassassin RE: blocked spam and blocked viruses. Since 10.8.2, there are additional messages sent when the filter blocks a virus...