Hi.

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:: [email protected] Pfizer -75% now
Internet Message ID: <[email protected]>
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:  [email protected]

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?

Pleas help