Below are the Spirit Mail found in Kena: Bridge of Spirits.
Village
There are 3 Spirit Mail total in the Village!
1. This Spirit Mail can be found in a house just past the first barrier you removed with the mask. To enter the house, you’ll need to head to the left side and use the Rot to move a giant barrel to the white circle. Jump on the barrel to enter the house via the room. The Spirit Mail will be located in the golden bag on the table.
Rusu Mountain
There is 1 Spirit Mail in Rusu Mountain!
1. Hidden in a mountain above the waterfalls just past the Ruins warp shrine