Does not work as you type, you have to highlight all text and then select Sentence Case each and every time you write an email. This is not a replacement for Auto-Capitalize that has been a feature of Outlook for well over a decade. It should be an option in the Editor or Auto-Formatting.
There are many other threads about this and nothing is happening, can't you escalate to a dev that can actually sort the issue and give us back this missing functionality we are all accustomed too?
Its a poor oversite tbh, most of the office have gone back to the old version because of this **** functionality.