In my public mail DMZ server, in my Exchange Management Console --> Anti-Spam tab --> Sender Filtering, I have added a our email domain there to block spammers using our domain email address. However, we have this 3rd party tool we need to make an exception that will use our domain email address and send email to us to our exchange server. So my question is: 1)Is there anyway to set an exception in our server in this DMZ? 2) Is there way I can configure it an exception just for this 3rd party tool to bypass the DMZ and go straight to our main exchange server that is in our domain? Thanks.

Whitelist the ip addresses of the servers you want to allow to send to your org.

Create a SPF record in your extrernal DNS. See http://openspf.org or http://www.microsoft.com/senderid. To allow a machine to send e-mail using your domain you only have to add that machine's IP address to the DNS resource record. Publishing your domain's SPF record helps not jut yourself, but also everyone else the uses SPF to detect "spoofed" addresses.--- Rich Matheisen MCSE+I, Exchange MVP