Outlook - Microsoft Report Message Add-on
Using this feature will help Microsoft learn our email environment and its detection capabilities when it comes to phishing/spam vs. legitimate emails.
In the outlook app, under the home tab, you will the Report Message option:
Highlight the email you are trying to mark as phishing, junk, or not Junk and click the Report Message Drop down menu and select option that best suites what you are trying to do: