When Discord submits a formal complaint to the Equestrian Postal Service, he says if the next mail delivery doesn't arrive in a timely fashion, he will plant a baby chaos monster in all the mail and packages delivered throughout Equestria!

It's up to Gabby and Derpy to try and save Equestria's only mailing service. Will they make it? Will they make it BACK? Will a giant purple monster take them away and keep them there... forever?