exchange 5.5 spammed to death

I am running a ex5.5 srver on Win NT 4.0 box.
The server is getting spammed in the outbox of the imcdata in exchnge folder. I followed microsofts recommendation to shut off relay, it still spams, I took the sever off the network,
clean out the outbox the when i start the Internet
Mail services again the outbox fills up without being on it being on the network. Strange stuff.
How do I stop the queue filling up. I have done all the popular techniques. Help.