How do I mail a postcard?

In Pikuniku a friendly ghost asked me to send a postcard once in a while.

I've now found a postcard, and I've noticed various postboxes around the world.

But I can't for the life of me figure out how to put the card in the box. Someone please explain this to me.

2 Answers

The developers said on twitter that "You can’t send the postcards."

found your question while searching for the answer myself. Found them on Twitter saying you can't send the postcards. We cannot be nice to ghost. :,<

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