Postal incumbents in Europe have encountered during the last decade fundamental changes in their industry environment, which now threaten their very business model: governments decided to liberalise first the parcel market, then gradually the letter market so as to introduce competition. Substitution by electronic means led at the same time to a decline in mail volume. As a consequence, incumbent operators are losing market share in a declining market, whereas new revenue streams would be needed. International and product diversification have become important strategic moves, which can be found among all players. This dissertation therefore examines these diversification strategies with the focus on diversification of postal incumbents into the logistics business. The methodology consists in the application of theoretical concepts to the research question and subsequent confrontation of the findings with expert interviews and the current economic reality. After a competitive analysis of postal incumbents and after a logistics industry analysis, the dissertation carries out strategic analyses for diversifying postal incumbents: it starts out with critical success factors and assesses the attractiveness of the logistics industry, the costs of entry and possible synergies for postal incumbents. The results show that the logistics industry is sufficiently attractive, that the costs of entry are sufficiently low and postal incumbents can profit from relatedness with their historic business to succeed in the business. Relatedness can be found when sharing infrastructure and technology (product relatedness), in network management skills (managerial relatedness) as well as in marketing and sales (customer relatedness). Information technology, network and supply chain management skills, customer and market know-how, area coverage and density, as well as brand/trust are specific critical success factors and therefore relevant for postal incumbents to successfully enter the logistics industry. Within the framework of a SWOT analysis, the following dimensions were tested whether they form strengths or weaknesses for postal incumbents in the logistics industry: products and services, infrastructure, organisation and structure, human resources, and financial performance. Most strengths are valuable resources, but not rare and also imitable or substitutable (resource-based view). Postal incumbents should focus on the quality of their products and services, customer confidence and loyalty, as well as on opportunities for economies of scale in order to outperform traditional logistics operators. As far as strategic groups are concerned, European postal incumbents can be grouped by how their logistics business is positioned and by the share of their logistics turnover compared with total turnover. Both mappings show that German DPWN is the only global player that also operates its logistics businesses completely independently from the core business. Another strategic group includes mainly Nordic postal incumbents that operate on a regional level through an independent logistics business unit, generating a substantial part of their turnover from logistics. Smaller, nationally operating incumbents often add logistics around their core services (mainly letters) whereby the turnover from logistics accounts for a smaller portion of total company turnover. As a result of the analyses, the following set of generic strategies for European postal incumbents aiming at a diversification into logistics can be formulated: "National Hero", "Selective Geographic Expansion", "European Network", "International Player", as well as "Lead Logistics Provider". Logistics business is indeed a promising area of diversification for postal incumbents: the logistics industry is however highly competitive, with very low margins and has not revealed lucrative niches, which could be quickly covered by postal incumbents. Although the market is growing steadily, there are not that many innovation or significant dynamics that would trigger convergence or create new business opportunities for new entrants.