sudden change in font size when reading messages

HELP!  Please!
eM Client came pre-loaded on my Asus and I’m up to date. Have been satisfied with the program until yesterday when the font size for reading messages suddenly changed to something like 8 point or smaller . . . totally unreadable.  I’ve gone to settings > Mail and tried to reset the font size.  This does nothing, even if I ask for something like 24point Bold.  Messages remain unreadable.  HTML images from commercial/institutional posts are also shrunk beyond readability.

try pressing Ctrl+0 (zero) to remove any zoom settings.
Holding ctrl and + or - or using the scroll mouse button can zoom in or out on the messages.