Open Relay/Spamming Help

Hello All. I am fairly sure one of the server I monitor is being used to relay spam and I'm not too happy about this. The server is running Small Business Server 2003 and I was wondering if there was a way to fix this problem.

Do I change the port my email comes in?

This is new to me so any help would be great!

Thanks

 

I do have an exchange server. We use Trend as our A/V.

We keep getting emails from our server saying we have several emails that aren't going out. In our system manager there are several emails that are stuck that are not from any of our customers and not to anyone we would send too.

 

OK any suggestions on what filter might be better than another? We have a pretty vanilla setup so anything I'm sure would help.

Would a filter protect against someone using this machine as a relay though?

 

Well it turns out I was wrong. The server was not being used as an Open Relay. I wanted to test it again and found this article from Microsoft.
http://support.microsoft.com/kb/324958
It was pretty simple and it says it isn't open.

So this means it might be an employee so now I get to investigate that. Thanks for all the help.