It does sort of work, but you need to highlight the text first, and each and every time, as it won't stay as the default.
It's just another annoying/unnecessary step though, no substitute for auto-formatting the capitals like in old versions of Outlook, just needs to have the option to set the Sentence case formatting as default really, as 99% of people will want to use it in emails and are used to the old behaviour. Surely this is a simple change.
**** knows what MS are doing, probably adding more data logging(stealing) **** instead of the stuff users actually want.