Step 1 - Open the e-mail that you want to report as phishing. The e-mail needs to be forwarded as an attachment to firstname.lastname@example.org
Step 2 - As per the image below, Click Message, then click More then click forward as attachment
Step 3 - As per the image below, put the following address in the To... field: email@example.com and click Send
Please note - once you have sent your e-mail in Microsoft will automatically analyse it making them more efficient in detecting these phishing e-mails. You will not get a reply or response from this action from Microsoft, the process is automatic once forwarded.