While writing an email tonight I mis hit some combination of keys.  It changed the visual view of the email.  The actual font of the email is unchanged, but it now displays much smaller.  I tried:  changing the font and changing it back, saving the draft and re-opening it.  Existent email in my various folders still display as I want (i.e. larger).

This appears to have made a change that is 'sticking' - starting another new email gave the same small display.

FWIW:  I was trying to hit Control + U - for underline, but hit some other combination.  An undo also didn't change this.

Thanks