Using New Outlook on Windows for personal email, calendar, and contact management
You need to Enable Text predictions, Enable auto correct, and Enable auto capitalization within Microsoft Editor Settings.
- Compose a new email and pop open in a new window.
- On the ribbon bar left click on Select Editor > Editor Settings.
- Click on the
Enable auto capitalizationto enable the option.
Credit to Ramhound from another website: https://superuser.com/questions/1847147/how-to-disable-auto-capitalization-in-new-outlook