I’m in the happy position of not needing—indeed never have been needing—to use Outlook for my email. Others, sadly, are not so lucky. Karl Voit points to a remedy that allows you to compose your email in Emacs and send it via Outlook.
That’s nice but it got me wondering if something like mbsync could be leveraged to solve this problem. Ben Francom has a post that describes using mbsync with Outlook365 to handle his email with Mutt. Of course, once you get mbsync dealing with Outlook, a large array of solutions are possible. You could, for example, handle your Outlook email with mu4e or any of the other Emacs based mail clients.
As I say, I’m not and never have been an Outlook user so I don’t know how well these solutions work and what the gotchas are but if I were, I’d sure be looking into them. If you’re constrained to use an Outlook account, you might find the two links above useful.