Using classic Outlook for Windows in business environments
I haven't - the promised button in Outlook has never appeared for me, so no way to report phishing or brute force attacks on my account
To Nick,
Try this in www . Outlook . com in a Windows computer.... (not the application or the mail app).
- Click / Select the offending email.
- Report - will hilghlight when an email is selected
- Report Phishing or Report Junk
Good luck.

