I am currently studying Middle East Political history and have come to some correspondences between British diplomats and Arab leaders. The dates on these outgoing correspondences are 14 July 1915, from Cairo, (British administered) Egypt and 30 August 1915, from Mecca (modern day Saudi Arabia). My question is threefold.
How long would it have taken an official correspondence between officials to reach one another given the above region of travel?
What would have been the means of delivery for these correspondences? -Diplomatic Couriers?
What was the means of postage between countries in the early 1900's?