Sorry I am a foreigner,not from the U.S.A. so I never realised large
print to assist those with eyesight problems was regarded as screaming
in the U.S.A..
Large print and use of caps are quite different issues. Those with
vision problems have choice of typeface and size for e-mail regardless
of the client used. They need not go to the extreme I chose, designing
my own typeface to maximize clarity and readability since so many fonts
are available within Windows or OS.