Use the Report Message button on the Outlook desktop application ribbon.
- Phishing email tries to lure you into giving away personal information. If you feel an email is attempting to do this, report it as Phishing. See Identifying Phishing Attacks and Properly Combating Them.
- Junk or spam is unsolicited email, usually trying to sell you something. If you signed up for it by registering for a website or service from the sender, it is not really junk, and you should unsubscribe following the instructions that should be at the bottom of the email.
You should also see the Report Message button in Outlook for Mac OS and Outlook on the Web (https://outlook.office.com).
The Outlook mobile app for Android and iOS provides a Report Junk menu option from the menu while viewing the suspect message.