Cans tied together with string -if the string is long enough- might be the number one answer. Or how about Cave Paintings? Cave Paintings are the OG. Pretty difficult to send big bits of rock and stone to a loved one overseas, though. Hieroglyphics on papyrus? Getting closer…
The answer I’m thinking of is Homing Pigeons. Used by Egyptians in 3000 BC for military communications, homing pigeons became a way to communicate many things throughout history, including the winner of the ancient Olympics, news and stock prices (the origins of Reuters!), stuff Ghengis Khan wanted to tell his military, and more. Even once planes were on the scene, pigeon post was still seen as superior to sending secret or sensitive messages across long distances. These clever birds would be trained to fly from nest to nest (which were placed where people needed to send and receive messages). The post could have been anything from location coordinates to microfilms.
How did they do it? The thing is, homing pigeons are actually really smart and have a magnetic compass (that they can use to navigate the Earth’s magnetic field), which gives them a sense of direction even when they can’t see the sun. But the really cool thing is that they have an internal olfactory map - i.e. they navigate by smell! They literally follow their nose … which is even stranger because pigeons don't have noses - but you know what I mean.
These days, the postal service can handle pretty much anything you throw at it, so thankfully, there’s no need to rely on our little feathered friends. Pigeon letters, are a multi-combo set you can write on, fold, and send, directly with one sheet. A bit like origami mail. Coming in fourteen beautiful patterns, they are the easiest and most lovely way to dispatch handwritten notes. No sniffing required.