Windcat Ltd. was a massive parcel mail service adapting windcats as its primary postal vessel. Its period of operation included the Great Monster Uprising, when it was used by almost all adventurers. Books, at least, were required to be wrapped in Windcat Courier approved brown paper before being sent.

The postal service was said to be able to track down any addresse, no matter their location or how hard they tried to hide. There was a legend that they once found an escaped prison convict who was hiding in a cave up in the Flathead Mountains and delivered the huge parcel which he had been sent. The parcel contained three guards, who promptly arrested him again, so customer satisfaction probably was not high on their list of priorities.

SOURCE(S): Legends of Zork