Microsoft has updated his junk mail reporting add in for Outlook.
This new version is now compatible with Outlook 2016.
When you report a message, the report is being sent to Microsoft for further analysis.
You can download the add-in here https://www.microsoft.com/en-us/download/details.aspx?id=18275
Then just select the version you want to install
Close Outlook and follow the wizard to install it. No specific configuration
Once install, the add in is shown in the toolbar; just select the message you want to report as spam (junk) or phishing mail