Description
There are a number of ways to report emails as Phishing, however the following should be the common way that will work in all instances
Process
Whilst in the MS Outlook client:
With Reading Pane enabled: Click on the email and the Report button will be enabled, click and select report as phishing.
With Reading Pane off: Open the relevant email and the Report button should now be available, click and select report as phishing.