If a person finds a letter addressed to his brother, is it permissible for him to open it?

The questioner : If someone finds a letter for his colleague, a letter for his colleague that came from above, and he opens it and reads it, does he commit a sin?

The Shaykh : Is it addressed to him?

The questioner : Yes, it is addressed to his colleague.

The Shaykh : Addressed to him?

The questioner : No, it is addressed to his colleague.

The Shaykh : No, no, if a person finds a letter addressed to his friend or his colleague, it is not permissible for him to open it unless the sender has said to him: If a letter comes in my name, you may open it.