Contacting all guests about an unexpected closure
If you need to let all your guests know about an unexpected closure you can find all guest contact details for the relevant dates using either the Guest List report, or for more options, the Booking Forecast report.
Once you have those details you can use a marketing/communications platform (or email app) of your choice to contact your guests all at once.
If using an email app, make sure you only add email addresses to the BCC field to ensure the email addresses remain private.