Public forms & Email In — Choosing what lands where (2)

Some fields can't take a value from email, and the picker says so instead of letting you find out later: anything RowFold works out itself (Auto number, Formula, Lookup, Rollup), a Doc, which is written on its own page, and any field a lifecycle or approval policy governs — those decide their own value, and an email must not talk past them. A saved mapping is checked again every time mail arrives, so if a field is later retyped the mapping stops running and the page tells you why rather than writing something wrong. The panel at the bottom shows what the last email you received actually contained, so you can pick sources against real values rather than guessing.