If you are sending a message a short way, drop it in mail and let the Netherworld Post Office dispatch a bat to pick it up and carry it the way. Speedy, bats are able to carry light notes and cards much faster than conventional means.
Questions have arisen regarding their ability to see (and if the address need be written upside down) — please do not worry. The Post’s bat carriers know what they are doing. Service with a fanged smile!