This document discusses the history of letter writing theory known as ars dictaminis from antiquity to modern times. It analyzes how contemporary business textbooks teach letter writing by focusing on structure, grammar and conventions over rhetorical considerations and design. The document proposes recasting the classical rhetorical canons as a heuristic for a multimodal approach to letter writing in the 21st century. Elements like arrangement, style and delivery should consider visual design and medium in addition to language. This reframing could help make letter writing instruction more relevant to digital correspondence.