The t-online username can be one of atleast 2 formats: Anschlusskennung#TonlineNummer#mitbenutzernummer@t-online.de or AnschlusskennungTonlineNummer#mitbenutzernummer@t-online.de

e.g. Anschulsskennug: 001876543248, Tonline nummber 560235483283, Mitbenutzernummer: 0001

Would give a username of 001876543248#560235483283#0001@t-online.de or 001876543248560235483283#0001@t-online.de without the # between the Anschlusskennung and TonlineNummer

Using this you can also avoid installing the awful t-online supplied software on your PC even if you don't have a seperate router! If you are lucky your router will have support for t-online and will have seperate dialog boxes for Anschulsskennug, tonlinenumber etc.

Please note the various credential numbers in on this page are random please do not try them though as TCOM may block your connection if you send the wrong credentials 3 times in a row.