This bug was fixed.
- I sent something to the Geo Council but it never came back
- I requested a postcard but it never arrived
- I have collected all the decorative easter eggs but never got an easter bunny.
Unclear but the bug seems to occur if you request something and then go to another lot or close your game without waiting for the stuff to arrive.
In most cases selling the mail box and putting a new one seems to help solve the issue as long as you don’t leave your lot.
Go to build mode and delete your mailbox (this is possible since Patch 1.5.139).
Search for mail box in your search field.
Pick one and place it in your game.
Close the game completely and restart the game (don’t just go to the main menu but completely exit the game)
How to prevent
To prevent this bug, try to stay on your lot until you got the things back.