At first glance it looks like it wants you to specify the mbox you will be using somewhere however I believe the mboxes are auto-generated by AEM and have a long non human readable alphanumeric name. I would recommend reaching out to AEM ClientCare team. You can get to them via: https://daycare.day.com/home/createaticket.html
Mihnea Docea | Technical Support Rep, Customer Care | Customer & Employee Experience | Adobe | (:: 1 (800) 497-0335