You can create an email template that entices members to come back to class, then attach it to a Days Since Last Attendance Alert.
Under Attendance Alerts, you can create two kinds of attendance alerts:
1 - Attendance Alert Count: Use this one to congratulate members on X number of classes/workouts.
2 - Attendance Alert Date: Use this one to entice members who have stopped coming to come back. Use this one for At-Risk Members.
Step 1: Create the Email
Go to Messaging > Email Templates > Attendance Alert
Click Add New Date Template
Create the email you'd like to send and click Save Template
Step 2: Set the Alert
Go to Messaging > Alerts > Days Since Attendance
Click Add New Days Since Last Attendance
Enter in the number of 10 since the member's last attendance when you want this email to go to the member, then select the email that coordinates with the number of days missed.
Pro-Tip: You can create a campaign to gain the member back by creating multiple alerts/emails that all send at different times. For example, send one email at 10 days then another at 30 days, etc...