The general post office has its beginnings in scripture.
Jeremiah 51:31, "One post shall run to meet another, and one messenger to meet another, to shew the king of Babylon that his city is taken at one end..."
A "post" is another name for a courier:
2 Chronicles 30:6, "So the posts went with the letters from the king and his princes throughout all Israel and Judah,"
Esther 3:13, "And the letters were sent by posts into all the king's provinces..."
Scripture records messages being sent "by the hands of messengers"(1 Samuel 11:7) from as far back as the book of Job, which is the oldest book in the bible:
Job 1:14, "And there came a messenger unto Job, and said, The oxen were plowing, and the asses feeding beside them:"
These messages were delivered using the current means of movement at the time:
Esther 8:10,14, "And he wrote in the king Ahasuerus' name, and sealed it with the king's ring, and sent letters by posts on horseback, and riders on mules, camels, and young dromedaries: So the posts that rode upon mules and camels went out..."
In times passed, people sent messages to others by posting their letters on a "post" in the middle of town, with the name of the one who it's intended for. People would go to this "post" and look for letters with their name on it, and if they saw their name on a letter they would take it down from the post and read it. However, due to theft of messages, an office was built around the post to prevent people from stealing messages. This office became known as the general post-office. People would then go to the general post-office to pick up their messages