Advertising letters are among the most successful and most frequently used means of direct marketing and differ significantly from other formats both in terms of language and text design. After a short description of this text genre and a look at its advantages and disadvantages from an economic viewpoint the paper deals with the typical linguistic and typographical forms of offline and online advertising letters and their rhetorical strategies. With regard to offline advertising letters, it is argued that the pattern of another genre, namely the business letter, is imitated and the related appreciation is made useful. This becomes apparent in the design of the envelope and runs through the entire linguistic and typographical structure of the cover letter. However, online advertising letters belonging to email marketing do not imitate any text genre but follow the pattern of websites.