Yes, you can absolutely send announcement emails to waitlisted guests.
To start, create your announcement email. For best practices on how to create an announcement email, please refer to Sending Announcement Emails.
Once you've composed your announcement email and determined a launch time, you will click SELECT RECIPIENTS BY TYPE / TAG.
A pop up window will appear. Simply check the box next to the groups you want to receive the announcement (in this case, waitlisted guests) then press SAVE SELECTION.
After pressing SAVE SELECTION, the group that you selected will be visible under SELECT RECIPIENTS BY TYPE / TAG. Simply press LAUNCH whenever you're ready for the email to go out.
Thank you! Please contact SeatRobot support if you have questions about this or any other SeatRobot features.