This dream reveals a desire to receive something that is able to change our current situation. If the envelope contains something unpleasant or empty, it indicates fear. If we write a letter, and it is hard for us to do so, it also reflects fear. Breaking or burning the letter symbolizes break up with a friend or a relative. To receive an anonymous letter, it means there is something that disturbs our conscience. If it is unreadable, it shows disagreement or missed appointments.
Dream dictionary: Letter, mail dream meanings
…If you dream of a letter-carrier coming with your letters, you will soon receive news of an unwelcome and an unpleasant character. To hear his whistle, denotes the unexpected arrival of a visitor. If he passes without your mail, disappointment and sadness will befall you. If you give him letters to mail, you will suffer injury through envy or jealousy. To converse with a letter-carrier, you will implicate yourself in some scandalous proceedings….
…To see a United States mail box, in a dream, denotes that you are about to enter into transactions which will be claimed to be illegal. To put a letter in one, denotes you will be held responsible for some irregularity of another….
The dream in which you receive some letter or any other kind of mail, means that you will receive some news. The dream could also mean that you wish to know something you dont know yet, therefore you wish someone to tell you about it.
In a dream, a mailman represents the caller to God, a preacher, a news carrier, an emissary, a letter carrier or a courier. (Also see Dromedary rider | Mail | Ostrich)