If in doubt, throw it out!
Opening a malicious email can cause problems to your computer, loss of data, and corruption of files. Opening a malicious attachment could also do a number of undesirable things such as installing a key logger to record your keystrokes, installing a virus, or even providing an intruder with remote access to your computer.
Not only is malicious email risky to your machine, but it causes problems to other computers connected to the same Internet connection. It’s not worth the risk to open emails that you are uncertain from where it originated.
Concerned about deleting something important? Typically, a sender will follow-up with you if they do not receive a response from you.
For more information, visit Pepperdine University’s Information Security page.