To dream of reading someone else’s email messages signifies that you are mistrustful of others and you tend to poke your nose into friends’ business. Perhaps you have recently stumbled upon some information that was not meant for your eyes. [1]
An actual, imagined, desired, or feared message.
A desire to communicate with a particular person, or to feel more heard in general.
Help or support (or a desire for it).
Consider also the content and timing of the email, identity of the sender and receiver, and how you felt about the message.
See also: Communication, Computer, Texting, Voicemail, Typing, Words, Phone [2]
If we are sending an email in dreams we have information which others may need. [4]