i think you want zimbraPrefMailLocalDeliveryDisabled
i find usually if theres soemthing in the ui that i want to find the cli option for, i do like a zmprov ga accountname and pipe it to a text file. then i make the change, and do it again piping to a second text file. then just diff the two files to see whats changed.
Thanks ! . That is what i was looking for.