I have an Exchange Server 2010, that uses a smart host to send out mails. A day ago the owner of smart host contact us and told us that we send out spam.
I have try different open relay test on the net and all of them come back saying that this server is secured and can not be used as relay server. But I can see in my Exchange Queue Viewer that it keeps coming in new messages. Here is an example of how it looks.
Identity: mailserver\3874\13128 Subject: Olevererbart:: firstname.lastname@example.org Pfizer -75% now Internet Message ID: <email@example.com> From Address: <> Status: Ready Size (KB): 6 Message Source Name: DSN Source IP: 255.255.255.255 SCL: -1 Date Received: 2010-12-09 21:46:22 Expiration Time: 2010-12-11 21:46:22 Last Error: Queue ID: mailserver\3874 Recipients: firstname.lastname@example.org
How can I secure our exchange server more, to stop this from happening?
Could I have got an virus that hooks up to our exchange server and send mail throw that?
As I can see the From Address is always <>, is there someway that I can stop sending mails that don't have a from address that I describe?