underscore characters no relation emphasis
"Simulated" underlines in plain-text
In plain-text applications, including plain-text e-mails, where emphasis markup is not possible, the desired emphasis is often indicated by surrounding words with underscore characters. For example, "You must use an _emulsion_ paint on the ceiling".
Some applications will automatically add emphasis to text manually bracketed by underscores, either by underlining or by italicizing it (e.g. _string_ may render string or string).
no relation