For the benefit of my German readers I want to share some of my experiences with trying to end a contract with 1und1, a part of the United Internet Group (other parts are GMX, Web.de and Schlund+Partner); After my experiences in the last days (some of them are described below) I can only recommend to stay away from United Internet.
First step: "Vertragshotline" (hotline for contract issues) - thats around 1,92€ a minute (mobile phone, its slightly cheaper from a landline) for the chance to listen to bad music - it took them 20 minutes to make things worse.
Next step: trying to figure out a fax number that I could use to fax the cancellation - too bad, seems like they have forgotton to put that on their website. Even worse that fax numbers for 1und1 that you can still find on other web sites are not working anymore (can this be a coincidence?)
But there is a special web site: vertrag.1und1.de that you can use for contract cancellation. Thats nice, so I select my contract, they tell me "please do not end the contract"... alright ... then force me to answer a questionaire about my reasons to cancel (you have to fill it out for the process to continue) and then tell me that "for security reasons"* I get an authentification code that I have to tell to the people on the service hotline that I need to call in order to get a code that will allow me to download a form that I have to sign and send to a Fax number that I'll find on this form, WTF? Luckily I live pretty close to 1und1 and will just bring it there personally - but from what I read on other internet pages - I expect them to ignore the letter anyway.
So, anybody thinking about making a contract with 1und1 should be aware that this seems to be a lifetime commitment (at least).
* read as: to secure their profits (and they are making big profits, last year they had a 12.5% profit margin)