Which messages did British, Dutch and French postage stamps carry during colonial times in Southeast Asia?

Dr Robert Casteels explores  the agency of Southeast colonial postage stamps. Invented in England in 1840 postage stamps correspond to the last chapter of the lost world of colonialism. Each colonial power ran its own postal service for its colonies. Which messages did British, Dutch and French postage stamps carry during colonial times in Southeast Asia?  Casteels choses to focus on these three colonial powers, ignoring British Burma, Spanish and American Philippines as well as the Japanese occupation.