Er, turn off your open relay as a starter. What you described is typical open relay performance. And of course it taints you. The spammers are simply relaying off your system. Until you stop the spam relays you have no leg to stand on.
...Or maybe he has particular users whose accounts on his server forward to an AOL address. As described later in the message.
-- Kelson Vibber SpeedGate Communications <www.speed.net>