How do you remove the "reply to" option in email?

How do you remove the "reply to" option in email?

How do you remove the "reply to" option in email?  I seem to have managed to set up an option whereby every time I compose a new email there is the option to have the recipient reply to a different email to my ZoHo one, which I don't want.

I have to click the drop down arrow and select my ZoHo email every time, so I want to remove this option, but cannot find out how to do it anywhere.....