Good luck with that. I had the same issue. After talking with Comcast support, they told me that the internet provider in France would have to look at it. right! So, I set up a Gmail account for emailing to France and haven't had any issues since.
Did you click on the link which tells you what must be done?
Need Email Help? Please post the following information in your post. Do you use XfinityConnect? The Full or Lite version? Do you use an email client? Which one? (Eg; Windows Live mail, Outlook, a smartphone etc.) Which browser/version do you use? And- have you cleared your browser cache? Which operating system? XP, Vista, Windows 7, Mac OS X Details of the problem you are having.
COMCAST has been denying traffic from Wannadoo and Orange in France for a long time. They claim excessive spam. Other ISP (G-mail, Surewest, AT&T) will transmit same traffic. Give it up and go an alternate route.