The official blog for Windows Server Essentials and Small Business Server support and product group communications.
...It's old technology. When it breaks, it's hard to troubleshoot (hint - it's the hardware). When it works perfectly, nobody thanks you. If it's not set up correctly, the entire office will let you know. That's why you need this guide:
http://www.microsoft.com/downloads/details.aspx?FamilyID=1b7510a0-1595-4776-a101-c3bec7512594&displaylang=en
The document is what it says it is - a step-by-step walkthrough for setting up and configuring fax on your SBS server.