Here's why:
* Envoy specifically refers to a person sent as a representative or messenger, often on a diplomatic mission.
* Other words might be associated with being sent, but they have different nuances:
* Delegate is someone chosen to represent others, but not necessarily sent on a specific mission.
* Messenger implies delivering a message, but not necessarily being sent as a representative.
* Emissary is similar to envoy but can sometimes have a more informal connotation.
Therefore, envoy is the most accurate word to describe someone who is sent, especially on a formal or diplomatic mission.