I have an e-mail in my inbox from United Parcel Service and the subject is UPS Notification.?

There is an attachment. I'm afraid to open it because a couple years ago an e-mail came around saying we should not open any e-mails from UPS. They said it was a virus. What should I do? I'm afraid to open it and also what if it is real and maybe I need the information. Please tell me if I should open it or NOT. HELP.