I’d start with this part of the response you received: You must enable either manual, POP3 polling or have a custom mail poller enabled before enabling reply by email
That makes it sound like maybe you haven’t set up POP3 or mail-receiver before trying this. (You probably want mail-reciever.)
I’m not even sure where you might have found those Rails commands, because both of those processes would have you use the Admin site settings:
