I cant read all of my yahoo email because it gets cut off at the edge of the screen.?

This does not happen on all emails in my yahoo account but I have been having this more often lately. When I open an email to read, the doent is wider than the screen. If I open the email in "printable view" I can then see all of it but still have to scroll back and forth to see all of it . How can I fix this? I am sure it must be in the settings somewhere but I am not sure where.