-- William Gibson, All Tomorrow's Parties
This is somewhat depressing. I took a few minutes this morning to play with SpamStats on work's mailserver.
These stats start at 0630 Jun 02:
Total number of emails processed by the spam filter : 60038
Number of spams : 43548 ( 72.53%)
Number of clean messages : 16490 ( 27.47%)
Average message analysis time : 3.61 seconds
Average spam analysis time : 3.37 seconds
Average clean message analysis time : 4.17 seconds
Average message score : 7.02
Average spam score : 10.43
Average clean message score : -1.20
Total spam volume : 102 Mbytes
Total clean volume : 69 Mbytes
It's also a default, non-tweaked install of SpamAssassin, so I would wager somewhere between a third and half of those "clean" messages really aren't.
My next step is going to be finally throw a.mx at our colo and have it dump anything over a 7, then relay the rest to b.mx at our offices.