In 1988, Dommermuth founded United Internet, and has been its CEO ever since.
Dommermuth owns 40% of United Internet, the Germany-headquartered broadband provider, which manages the 1&1, GMX and Web.de brands, with 2015 turnover of Euro 3.7 billion, and 48 million customers in 11 countries.
In 2017, when federal elections took place in Germany, the largest donation to a political party was provided by Dommermuth, Euro 500,000 Euro to the CDU, Germany's conservative party.
