1&1 is a recognised internet service mainly active in the marketing, IT, and hosting sectors. Montabaur, Germany is the location of their head office.
At present, Product Development, Project Management, and Web Development are frequently searched for professions at 1&1. They recruit for offices in Karlsruhe, Munich, Montabaur and 3 other locations within Germany. See below for a list of 89 open positions at 1&1, for instance "HR Business Partner (f/m)" and "Expert Agile Coach (m/f)".
On Wikipedia, there is a well-written description of 1&1, and also worth mentioning is their social profile on Twitter. A resource not to neglect is the company's careers page with more information about open positions and career prospects.