This fourth volume closes the Epistola series, which brings together contributions from leading European specialists in the epistolary genre, an art form that interacts most with its cultural, social and documentary environment. The letter, as an interface at every stage of its life, reflects the mutations of Late Antiquity and the High Middle Ages, caused in particular by political fragmentation, Christianization and the diversification of Latin. Influenced by the context in which it was written, it adapts to its recipient by anticipation; transmitted, it has a pragmatic dimension, since its aim is to inform, convince and order; received, it can elicit a response and participate in the weaving of an epistolary network; preserved, its text is sometimes recopied, manipulated and inserted into a non-epistolary context.