Tree Mail

 is a cryptic message the survivors get before any game-related events such as challenges. Tree Mails also gives out clues about upcoming twists and other events. The term may either pertain their mail box or the message itself. There is also Treemail at Redemption Island.

Exceptions
There were some treemails that were not related to challenges or Hidden Immunity Idols.
 * In Survivor: Borneo, the Rattana tribe got a treemail to inform them about Gervase's newborn son.
 * In Survivor: The Australian Outback, Ogakor received a treemail to inform them that an accident at Kucha had cancelled the Immunity Challenge and Tribal Council.
 * In Survivor: One World, Salani received a treemail to inform them that the immunity challenge was cancelled but they have to proceed to Tribal Council that night.