For several weeks now, my NT 4.0 server running Exchange 5.5 began to receive thousands of unwanted messages in the outbound messages awaiting delivery queue. No system changes have been made.
I ran a full virus scan using Symantec Antivirus Corporate Edition 7.5. It didnt find anything.
I retested my server to verify it is not an open relay server.
I believe it may be a virus or trojan on one of the user machines. I have 1 central email server and 10 remote locations that connect to Exchange via VPN. Approx 200 users.
I have seen across the network viruses such as gaobot and goner, which may open ports for malicious use.
I scanned the server with Spybot S&D and Bazooka, but they found nothing.
If this is the cause, I would think the problems would be on the trusted clients, as opposed to actually infecting the server.
Any help would be greatly appreciated.