I've seen both versions, and whether they check or uncheck all of the other options (behaving like a radio button), both versions are overcomplicated nonsense.

I've seen both versions, and whether they check or uncheck all of the other options (behaving like a radio button), both versions are overcomplicated nonsense. The unsubcribe-all should just be a link or button with its own submit value or URL param (like unsubscribe=all). I don't know why people overcomplicate things.