Who were the scribes of the letters of the Messenger (peace be upon him)?

The biographers of the Prophet (peace be upon him) mentioned that among his scribes for revelation and letters were: the four Rightly Guided Caliphs, Zubayr ibn al-Awwam, Amir ibn Fuhayrah, Amr ibn al-Aas, Ubayy ibn Ka'b, Abdullah ibn al-Arqam, Thabit ibn Qays, Hanzalah ibn al-Rabi', Mughirah ibn Shu'bah, Abdullah ibn Rawahah, Khalid ibn al-Walid, Khalid ibn Sa'id ibn al-Aas, and Mu'awiyah ibn Abi Sufyan. Zayd ibn Thabit was the most dedicated and specialized among them in this matter, and he wrote all of the revelation. Abdullah ibn al-Arqam was his regular scribe for letters and replies. Zayd ibn Thabit used to write to kings and also transcribe revelation. Al-Zubayr and Jahm used to write down the zakat funds.