Illegible emails

I finally looked at a couple of NYTimes emails, both News Alerts, but one 
good and one bad.  WORD showed me that the good one used
CHARSET=US-ASCII and 7BIT and it enabled my choice of font, important for 
those with poor contrast sensitivity.
The other used charset=utf-8 and
8BIT, and disabled my choice of font.

Questions, please > Are there any standards that apply here, i.e. for 
emails?

What is the significance of those two different formats?  Why choose one or 
the other?

G F Mueden  ===gm===