Reporting SPAM or Phishing email
The best way to report phishing - and the easiest for you - is to use the tools built into Outlook Online. While viewing the suspicious message, simply click the Junk or Reply menus and choose Phishing as shown below with red arrows.
Then click the red "Report" button to submit the item. While Office 365 already quarantines email that is likely SPAM or Phishing, reporting a message helps Microsoft improve the service.
Additionally, you can learn how to block a distracting sender or manage the amount of messages you receive.