Quick setup of a snom300 with Telekom as Registrar The best I found was the following: https://telekomhilft.telekom.de/t5/Telefonie-Internet/VoIP-Desaster-geloest/td-p/2373435 But this took me quite a while to get it successfully applied to my snom300 desk phone. Find the 2 images with my settings, which finally worked for me; no further tabs changed. Notes: The 'Displayname' and 'Account' are two times the same phonenumber, which you want to use e.g. typically one out of the three phone numbers you got from Telekom. Note the international format. In my case, the 'Password' was not the given one from Telekom, but the one I had chosen. Use 'Zugangsnummer' as part of the 'Authentication Username', which forms that eMail. Ignore the 'Anschlusskennung' as it is not used nor required here, nor the 'Mitbenutzernummer'. Ignore as well your 'Kundennummer' as not needed here. Enjoy a quick setup of your IP phone .... <img src="/snom300_telekom_settings_tab_1.png" alt="Tab Login"> Latest Firmware Update for Snom300: http://downloads.snom.com/fw/snom300-8.7.5.44-SIP-f.bin