 Irfan Shahid, professor of Arabic and Islamic literature at Georgetown University, contends that dismissing the letters sent by Muhammad as forgeries is "unjustified", pointing to recent research establishing the historicity of the letter to Heraclius as an example.A letter was sent from Muhammad to the emperor of Byzantium, Heraclius, through the Muslim envoy Dihyah Kalbi, although Shahid suggests that Heraclius may never have received it.He also advances that more positive sub-narratives surrounding the letter contain little credence.