To dream that receive mail indicates that you need to communicate or re-establish contact with someone from your present or past. It may also represent messages from your subconscious or intuition. The mail may also be a pun on a “male” in your life.
To dream that mail is lost suggests that you are feeling isolated of left out in some waking situation.
If you receive mail from someone you don’t know, then it symbolises a message from your subconscious.