@coldacid It's certainly jarring initially. You can switch out of it in File>Office Account and switch themes. They refer to this theme as "black" and not "dark"... which seems odd to me as they refer to it as "dark" everywhere else in Windoze. MSFT Interdepartmental woke-ism?
@dan "dark mode" already has a recognized meaning beyond themes, that's probably the reason for the different name.
@coldacid I hear you. I was kidding around. FWIW I've actually left it on in Outlook. I have finally gotten used to it after a few days.
@dan it was on "Dark Gray" but "Black" is no better. Still has those horrible rounded-corner rectangles everywhere that make Outlook look like a cheap rip-off of the ST:TNG displays.