The article considers problems of forming epistolary culture; relevance of the study is conditioned by the growing role of written communication in the modern world. The research objective is to analyse typical mistakes and to identify the basic principles, observance of which helps to establish contact between written communication participants and promotes better understanding. The research material includes various types of letters (teacher ↔ student; teacher ↔ teacher). Scientific originality of the paper involves clarifying additional criteria to evaluate the level of written communication skills. The findings indicate that the level of epistolary culture influences not only the form and content but also the overall intonation of a letter.