smtp relay Exchange 2003

I have been hacked by the guest account being enabled.I have unchecked the box to allow all computers that authenicate to relay. I still see the ques filling up after I clear them. Does anyone have any step by step instructions to stop all the secure smtp relay that I am getting.
I have disabled the guest account and the bad mail folder is still filling up and the Exchange ques are still filled up.
I have exchange 2003 on Windows 2003 server. I have no viruses on the Exchange box. Mydoom did go in the Quarntine section of the Norton Corporate Edition. We have done scans and no viruses have not been found. Any help would be great.