Interdimensional Post Office
From Jenny Everywhere Wiki
The Interdimensional Post Office was an interdimensional institution, seemingly capable of delivering physical mail to any universe.
In December 2019, after he became stranded in the Land of Manik, Darius mailed invitations to all his worst enemies through the Post Office, having sent them to the Post Office's headquarters using a crude dimensional-transporter device. The invitations were then seemingly transferred by the I.P.O. to the mail-delivering institutions of the various locales, such that the invitees initially had no inkling that the sender had necessarily been from another dimension. (PROSE: The Frost King's Treasure)