Ab_epistulis
Ab epistulis was the chancellor's office in the Roman Empire with responsibility for the emperor's correspondence.[1] The office sent mandata (instructions) to provincial governors and other officials.[2][3]
Ab epistulis wrote in Latin (ab epistulis latinis) and in Greek (ab epistulis graecis), and composed the short responses to petitions on behalf of the emperor.[4] Holders of the position usually had a particular vocation for literary matters.[5][4]