One problem with plain text and modern clients, is that text is wrapped
at the senders end.
Normally to something like 72characters.
This is a huge waste of screen space where you may easily have 160 to 300
or more characters available on a modern screen.
Worse is when the sender has changed the default to something large, then
you often have to scroll left and right as well as up and down to see the
whole message.
HTML on the other hand allows for dynamic rewrapping of the text by the
receiving client.
The sentence before last was all one line.
Change the width of this window, it should rewrap the text dynamically.