System Reset Password Notificaiton

[KTheisen]

I see we can change the email notification that a password has been reset-sent to the person whose password was changed-but how do I modify the system reset email that says you have X days to reset your password before it expires?  I hate the format and people always ask if it's legit so I want to be able to brand it so it's less suspicious looking.  Does anyone know where I can do that?