If you don't want to put all your available rooms for sale on the internet immediately, but add it from time to time or have an allotment agreement with a portal, you need to check the days when the availability is over or has decreased below a specific limit.
☞ Docs: Allotment
This plugin allows you to set a limit to check availability, and at the same time to receive an email (daily or every 3, 7, 14, 28 days), with a report containing a calendar for each room. The calendar shows the days when the room's availability has reached or fallen below the set limit.