How many letters did the Messenger (peace be upon him) send, to whom were they sent, and who was the messenger for each letter?

Biographers mention that the Messenger of Allah, may Allah’s prayers and peace be upon him, sent ten of his noble companions with letters to kings inviting them to Islam. They were: Dihyah al-Kalbi to Caesar, Abdullah ibn Hudhafah to Khosrow, Amr ibn Umayyah to the Negus, Hatib ibn Abi Balta'ah to al-Muqawqis, Amr ibn al-Aas to the two kings of Oman, Sulayth ibn Amr to the two kings of Yamama, Al-Alaa ibn al-Hadrami to the king of Bahrain, and Shuja' ibn Wahb to the king of the borders of Ash-Sham.