If you receive an email from someone you don’t recognize that has an attachment, you should not open it. In fact, you should delete it immediately, without opening it or opening the attachment. Opening an email like this could mean a virus is being sent or a hacking attempt is being made. This is a common thing that these people do. If you blindly open attachments, you could be putting yourself at risk.
The good news is that most email systems have a spam folder, and that’s where a lot of these kinds of emails end up. Spam folders usually empty themselves at a set rate every month. Maybe once every thirty days, whether or not you have opened them.