Help; I'm drowning in spam!

I have used Thunderbird for years.  The Junk Mail adaptive utility has worked very, very well for me.  But starting about a month ago it has just died.  I get about 500 spam emails a day into my various email accounts.  Having used it for a long time, yes, I have adaptive junk mail filter selected, and move to my Junk folder selected.  But now only about 20% get flagged, and half those that TBird flags as spam actually move to the Junk folder.  I have set my server to do filtering; very little improvement.  It is also adaptive, in that if something gets through I can drag it to the Spam folder and the filter will learn from it (this is an IMAP system, so the server can see I have moved it into the Spam folder).  I have tried pretty much every spam filter service available that does not require I have all my email first go through their server, but maybe I need to throw in the towel on that.  Most recently I installed the Avast!! system, which claims to protect against everything including spam, but saw no improvement at all.  I could not see that it was doing any filtering at all, so I called Tech Support and it was clear that their technician's job was not to fix my issue but instead sell me a $180/year maintenance package (with the usual "clean up your registry") , and that then they would take an hour whilst logged into my system to "fix" it for me.

My resistance to server-side filtering at the domain level is that others in my company and family would be effected, but if it gets down to it I guess I would do that.  But I'm getting about 500 / day.