GuestUsage : Guests are free up to free_allowance distinct emails over the trailing window_days. Past that an Enterprise plan meters them (metered, four guests to one seat: billable_guests, guest_seats); every other plan and build admits no new email until the count drops. available is whether this deployment can have guests at all: false on the shared cloud, where guest access requires a self-hosted or dedicated deployment, and every other field is then moot.