Interdimensional Messenger Service
If you received or would like to receive your letter in analog form, you may be wondering how the interdimensional messaging system works in the Universe of the Three Portals (or U3P for short). At the moment, the Prince is in charge of getting the letters to Earth, so on this page we are going to explain what we do, how it works, and everything we know about it.
First of all, we obviously need someone on Earth to deliver the letters. The Prince is able to go to that planet whenever he feels like it, and he usually takes the opportunity of the trip to do us the favor of taking the letters to the terrestrial mail.
Simply, every now and then we get the exact information to send by terrestrial means through the Internet. Then, the Prince, or someone who is around, goes to Side B of the U3P, goes to the Sand Castle, goes up to the first floor (or second floor if you are from the US, apparently) and approaches the Bell Mailbox of the Lost Garden, which is where Cornelia sends the lost letters (that is, the letters that she does not know how to get to their final destination, because Cornelia does not have a physical body of flesh and blood).
Inside the Bell Mailbox, as old and rusty as it looks, a highly complex process of "analogicalization" takes place in which it decompresses the compacted information coming from a more subtle dimension, and converts it into a format and material configuration compatible with the bodies and minds of the physical terrestrial species (i.e. everything is decanted into text and image printed on plain paper, which makes the medium perfectly safe for manipulation by creatures with physical bodies, you can even leave it unsupervised around children and pets).
After that, all that remains is for someone to pick up the letter that corresponds to each person interacting with the mailbox. Then that person travels to the densest dimension of the Earth, goes to the nearest regular human post office, puts the sealed interdimensional envelope (safe for human manipulation) inside the paper envelope, writes the pertinent addresses, and leaves it with the mailers so that the letter can continue on its way to its final destination.
It is possible that in the process of analogicalization, creatures that just at that moment were fluttering around the letters out of pure curiosity may be condensed. Although you may receive letters with some creatures that left traces in annoying places, they are not dangerous at all and, therefore, we do not worry about finding out how to prevent them from entering the mailbox.
Needless to say, of course, no one opens the interdimensional envelopes, as they are private correspondence. If one had been opened without permission, a "read by unauthorized subject" sign would undoubtedly appear on the envelope itself. It is possible that someone might use the blank space on the postcards if they need to add some extra information... you will excuse us, but we need to keep the earthly envelopes as light as possible.