If I opened an email I didn't know, could I be hacked?

Episode 1350 (25:09)

Ann from Studio City, CA

Ann got an email notification from Yahoo in her inbox. She had a hunch it was bogus but didn't do anything with it. Can she still get hacked if she opens it but doesn't click on any links? Leo says that a bad guy has to get her to run a program. Leo says that opening the email is relatively harmless, so long as she doesn't click on any links.