Consists of mailers, flyers, catalogues, letters, offers and other advertising materials sent directly to people via postal mail. Along with e-mail marketing, it is a form of 1:1 marketing. Because these materials are highly targetable and because their impact has been relatively easy to measure (compared to other forms of advertising) via test/control designs, these campaigns have historically made use of segmented/personalized messaging as well as extensive testing of creative/content.