Outlook has a setting to automatically capitalize the beginnings of sentences. I turned that off. But it's been long ago, I forgot where that setting is. But I recall it was near the setting that enables smart quotes.
They even do it on the web version of Outlook. The setting to change it is 4 levels deep and two of the options are at the bottom of lists and labelled "more options".
On display? I eventually had to go down to the cellar to find them... It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying "Beware of the Leopard."
It's starting. Outlook is doing some kind of "autocapitalisation" to me and I have no idea how to turn it off.