Heratech

Tool to check setup of SPF records:
http://www.microsoft.com/mscorp/safety/content/technologies/senderid/wiz...

Web based (microsoft) tool: https://www.testexchangeconnectivity.com/

Downloadable program: https://store.accessmylan.com/main/diagnostic-tools

If you are having problems getting an Iphone to sync to Exchange 2003 read this:

http://www.it-eye.co.uk/faqs/readQuestion.php?qid=1

I had major problems with a SBS 2003 setup and the above all helped.