The History of Pokemon Mail
Since cars weren’t around, mail back in the day was delivered by pokemon, differing on the region.
Kanto used Ryhorn and Doduo as land carriers for thier relative speed and bulk. Lapras for sea, for the same reasons, and Pidgeotto and Fearrow for air mail.
Johto, having the same mail system, used the same Pokemon as Kanto, though Noctowl was used for late night packages.
Hoenn’s land mail was handled by Donphan, able to carry lots and travel long distances, whereas the sea mail was given to Wailord and Sharpido (very carefully). Air mail, if a short distance was given to Peliper, but long term air shipping was handled by Tropius.
In Sinnoh, land mail was delivered on Garchomp, though intimidating, it’s way of speed was perfect for the routes. Air mail was given to Staraptor or Yanmega, while sea mail was sent through Empoleon because of its ice breaking abilities.
Unovan land mail was sent through Zebstrika (called the Blitzle Express), and air on the back of Braviary. Sea shipping companies tended to stick to traditional ships and boats, but Swanna proved to be quite helpful at times.
Kalos used Gogoat for the longest time, with Ryhorn also used for the normal mail. In the air, Noivern and Talonflame were fast and able to cover the entire region. Avalugg was the key to Kalos exports as they would slowly follow the boats carrying supplies for the sailors.
Alola is and was such a small region that most mail was delivered on foot, but Poni Island eventually began using Mudsdale. The air mail had Vikavolt, with Wishiwashi covering the enormous sea routes.
Galar was one of the first to start using automobiles in daily life, but before that Copperajah could be seen piled high with parcels. The waterways had Drednaw going from town to town, and Corvisquire training to carry taxis were also tasked with airlifing the mail.
This post was compiled from headcanons shared with me by @0-astraldreams-0