I am running an Exchange 5.5 server with POP3 users. In the outgoing mail queue in IMS I keep getting outgoing messages with blank originators addressed to email destinations such as travelagentpromos4.net, e-marketingsolutions.com, bestoffers.net…All sounding like they are some type of spam going out. I have tightened the security on the box well however they continue to send the emails. I have reviewed my IMS logs which I cranked up to maximum since i noticed this and it appears that they actually authenticate in and send messages right from port 25. I have run tests on port 25 to very that authentication is required and that relay is also prohibited. Authentication was required in order to send mail and relay was prohibited. In IMS properties I have selected accept hosts only with Authentication, clients can only submit if homed on this server and clients can only submit if auth account matches subbmission address.
What else can I do? They continue to send messages and I am worried I will be blacklisted soon. Any help is appreciated!!!
Thanks
JM