Updated 01-2021: Better support for Mac OS, support for Microsoft Live ... the missing bit of functionality that Microsoft should have provided? With the MailtOWA extension installed, mailto: links will automatically open O365 Webmail / Outlook Web Application (OWA) / Outlook Live by default. That's it. Nothing fancy. No ads or any other nonsense. ... Built to satisfy my own needs, released for free because other folks seem to have the same problem. Enjoy! If you like it, leave a review. I need more internet points! A free extension by i❤️.ws Emoji Domains Source code: github.com/jonroig/MailtOWA