I am running Microsoft Exchange 5.5 on an NT Server machine. I have noticed that every time I look at the “outbound messages awaiting delivery” queue for Internet Mail Service, there are many (sometimes a couple of hundred) entries addressed to our own domain as well as other domains with no “originator”. I have checked and our mail server does not allow relaying so I know they are not being delivered. They try for 2 days and then are removed. Is this someone trying to relay through our mail server? Is there a machine on our network (I have about 20) with a virus or malware? Is this something I should be concerned about? If more information is needed, please just ask.
