Defining a Custom Dynamic DNS Server for spdyn/ securepoint

Hi I’m using Surf & Soho MK3 with WAN PPPoE quite successful since years.
I want to setup now dynamic DNS server to access my network during travel with always the same address.
I’m using securepoint DNS service with the address
Does somebody know which configuration I need for update ?
Username and password are clear but it seems to be I need special string for the URL ?