Great News!!!
http://clip2net.com/page/m0/400032

It worked. I created a new email address with my ISP. I asked them to change my smtp port from 465 to 25 (which they can & did).

I tested the email and it worked perfectly!!!

It would then appear to me that the problem was not my firewall, but rather my Exchange 2007 server. I suppose it doesn't matter which way it works, as long as it does.

Thank you all for your kind help.

-Todd