This feature allows adding a new condition to message automation - listing availability. Using this condition, automated messages will be sent only if the listing is available for a given number of days before/after the stay. You can choose the number of days, and whether the condition is for the exact number of days, equal or more to that number, or between a range.
For example, you can choose to send a special offer to extend your guest's stay only if the listing is available at least 2 days before/after their reserved stay. This is useful to be able to upsell and make use of unbooked days between reservations.