Spirit Mail is one of the collectibles that are found throughout Kena: Bridge of Spirits. There are typically a few scattered about each level. There are a total of two that can be found in the Forgotten Forest area. They are pretty difficult to spot if you don’t know where to look. Here are their locations.
God Tree Shrine
One of the two Spirit Mails that you will find is up in the trees. Around the center of the forest are a few trees with platforms running up them. Located the tree with the broken platform and flower. Use your bow to shoot the flower and get pulled up the ledge. Follow the platforms up into the trees until you reach the curved fencing that you will hang off of. Drop onto a large tree branch beneath it and turn around. You will see a flower in another tree. Use the flower to pull yourself over to the other tree and use the climbing ledges to reach the Spirit Mail.
Clear out the Water Shrine to unlock a Forest Tear. Use the Forest Tear to create a Rot Cloud and use that to destroy the nearby corruption. Move the stone block over to the wall with the drawings to allow yourself to jump up to the ledge above. There will be a pile of leaves. Face away from the pile of leaves to see a flower on a tree. Shoot the flower to be pulled over to it. Quickly use your bow to shoot the next flower behind you. After being pulled to the second flower, turn around again to see a third one. Shoot the third flower and you will be pulled over to where the Spirit Mail is.