Can’t send or receive any emails with one specific url in the body.

Any email with the following url address included in body is blocked both incoming and outgoing email:
(www.tedandbarbrealestate.com).
This is happening both in outlook 2003 and in the webmail client. using comcast as isp and web host.

when requesting a delivery and read receipt nothing comes back.

I am able to ping the web site from command prompt and the request is returned. Using a linksys router but dont see any issues there. This is a clients machine. The next test I am planning to try is to take the router out of the mix and connect the computer directly to the comcast modem. Will post results when tested

STUMPED!!!! HELP!!