If you receive an email you think is suspicious, you can now report it directly from within Outlook. This works for Outlook on Android, iPad, iPhone, Mac, PC, and in webmail. When you report a message it will be analyzed, and if it is malicious the message will be removed from any mailboxes in which it was delivered. Reporting the message will also delete it from your Inbox.

On mobile versions of Outlook, there is a set of three dots below the time the message arrived:

Tap the dots to open the options panel and tap the Report Phish button:

You will see a confirmation appear when the report is sent.