Post Office
What this means depends upon what you are involved with the post office for in the dream. It could have a connection with money as something you need. It is also a meeting place and where you can receive or send communications. It is like a central point where many things connect, so may suggest your network of physical and psychic connections.
This is often about a need to communicate or to receive communication. It might even at times show mind to mind communication, or your intuitive faculty. The organisation and people behind the mail and communication.
If you are waiting for money it could be about that. But many dreams in my database mention post office as a background for other events. So it might be worthwhile reading Settings in Dreams.
Post office can be a meeting place, or even a place for flirting or socialising. For some people it is a place of decision, where you wonder whether to communicate the thoughts and feeling you feel.
Useful Questions and Hints:
What was doing or hoping for in relationship with the post office?
Was I working there?
What are my associations with the post office?
See Magical Dream Machine – Active Passive – Features on Site – You are More than You Realise