Have them remove the email account at the friends house.

Here are the instructions for setting up Outlook Express with Comcast. Please follow the instructions fully.

http://www.comcast.net/help/faq/index.jsp?faq=Hot117686

If your parents want to check their email accounts (when away from home)

Here is a link they can use

http://www.comcast.net/

Then click on mail and login

Hope this helps.