Business and diplomatic messages were handled by the service equally. Well organised, it had its own  post-horses that were used exclusively for the letter service; at each stop the time of the receipt and dispatch of the post-bag was written upon the face of each letter.
Business and diplomatic correspondence were handled by the service equally. Well-organized, it had its own dedicated postal horses used exclusively for letter delivery; at each stop, the time of receipt and dispatch of the mail bag was recorded on the letter itself.