Microsoft Word converts dashes to emdashes if you type " - ".

Outlook used to do this. I'm using a Mac, and Outlook on the Mac is a different animal, so Outlook on Windows may still do this conversion.

Small correction:

To get an en dash in Word, type " - " (word space hyphen space word) followed by spacebar.

To get an em dash, type "--" (word hyphen hyphen word) followed by spacebar.

Which has been happening for over twenty years on taoofmac.com, for instance. It’s a reflex by now.