This extension permits to modify the notification sounds used by the web version of Outlook for new emails and calendar reminders.

To use it:
1) Go to a web version of Outlook (either https://outlook.live.com/mail/ or https://outlook.office.com/mail/)
2) Click on the extension icon to open the settings, and enable what you want to do – select a MP3 file for each notification
3) Make sure to activate "Play a sound" for both email and calendar in Outlook Settings > General > Notifications
4) Reload the Outlook web page