Reporting Spam Mail
On Mac and PC:
First, click on the message you'd like to report. Then click on "Home" in the upper left of the screen.
After clicking Home, you should see an option that says "Report Message" in the upper right side of the menu.
Click on Report Message, and click "Junk" to mark it as Junk/Spam.
Here's a picture of what it should look like on Mac and PC: