A courier has a resolve to deliver the message no matter what. 

Relentless Runner

Starting at 3rd level you you have learned ways to use your ki to augment your natural ability to keep moving when the going gets tough. You learn the following:

Unnatural Recovery. You can spend 2 Ki points as a bonus action to clear one level of exhaustion or to use up to half your total hit dice to heal yourself. 

Bounce Back. You can spend 1 ki point to escape from a grapple or non magical restraints. Additionally when prone you can spend 5 ft. Of movement to stand up instead of half your movement.

Resist. When you are hit by an attack you can use your reaction to spend 1 ki point to gain resistance to the triggering type of damage. This resistance lasts until the start of your next turn. 

Perfect Delivery

At 6th level you learn how to deliver the message exactly the way it was intended by the sender. You gain proficiency in the persuasion and intimidation skills. 

A Messengers Intuition

Starting at 6th level you have an unerring ability to track down the recipient of your message and communicate with them. You have advantage on any checks to track down or find the recipient.

Additionally you can spend 1 ki point to communicate telepathically with a creature you can see for 10 minutes. The creature doesn't need to speak the same language as you but must be able to speak or understand at least one language. 

Couriers Speed

At 11th level whenever you take the dash action or step of the wind feature you can add 2 to your AC until the start of your next turn. 

Additionally your movement speed increases by an additional 10 ft. and you ignore difficult terrain.

Final Message

When you reach 17th level you have learned how to delivery the message of finality. Whenever you make an attack and hit with a monk weapon or unarmed strike you can spend a number of ki points up to your wisdom modifier. For each ki point spent you deal two additional martial arts die as damage. 

Additionally if you score a critical hit using a monk weapon or an unarmed strike you regain 2 ki points.