Here is a very interesting piece of postal history:
A piece of registered mail postmarked Bombay, November 23, 1866. The postage of 10 1/2 annas includes 4 annas for registration. The 6 annas stamp of 1866, SG68, was a provisional made by overprinting ‘POSTAGE’ on a part of a revenue stamp. Placed aboard the steamer “Rangoon”, the mail crossed the Isthmus of Suez by the overland route (before the canal was opened) and was taken to Marseilles, again by steamer. This reached London by December 21, about 28 days after departure.
Today we have fast planes, which take a few hours to fly from Europe to India. Yet, it would sometimes take couple of weeks for a mail to reach the other end. Must say that the postal department and its process must have been extremely efficient at that time, irrespective of the time taken by the ships.
Photo Credit: By Fconaway at en.wikipedia [Public domain], from Wikimedia Commons