Almost every other morning, 1and1's webmail interface takes a vacation--it just stops working either from too many users trying to access their webmail interface or from server problems on their site. A nice long call to 1and1 gets you an answer, "yes, our service is unavailable but please bear with us." Why should we bear with you every other day? We're paying for a service, and it's not being provided.
If enough of their users call them to complain, then maybe they'll do something about it. Give them a piece of your mind 1and1 clients.
