If you use Hotmail and get a private msg from someone you know, you probably should NOT click on it. There’s a blue clickable link that reads “…so and so has sent you a Private Message in the body. It will probably lead you to a page that asks you to sign in again to your email account, at which point your email account will be hacked.
When I got one from someone I know, but haven’t been in contact with for some time, I first looked at the source code, and didn’t recognize anything. Then I Googled How To Send Hotmail Private Messages because I wanted to learn if it was really possible and how to do it, before I decided to open that email. I found many posts in my search that told me that the Private Message hotmail email is a phishing scam. Clicking on the link does send you to that re-sign in page.