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

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> - <word>" (word space hyphen space word) followed by spacebar.

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