Your 1and1.com account works. It costs much less per year than the cost of changing to any ISP's proprietary email. It is as reliable or moreso than many suppliers.
Don't waste your time and don't tie your corespondence to a particular connectivity supplier. You will be more satisified in the long run.
Note - Since sometime last century, I've changed suppliers multiple times and never changed my primary email address (or that of my spouse). 1and1.com is also a new supplier since they bought the mail.com business.
PS: The Comcast-supplied Outlook 2010 works fine on Windows 7 for comcastbiz.net (as does Apple's Mail.app on OS X).