Hi there, 

Welcome to Box Community and glad to assist! 

Unmanaged users are Box users who:

• Have unlicensed and unpaid personal Box service accounts that are acquired independently of an Admin or Co-admin and that do not belong to your Box organization.


• Possess email addresses from your domain or verified domains (domains owned or
  controlled by your organization).


• Collaborate on your enterprise content.

Note: Unmanaged users are not controlled or monitored by your Admin, Co-Admin, or your organization's security policies, meaning that they represent a potential security and compliance risk. Box advises you to convert them to managed users as soon as you can.

To get this information, you can visit About Unmanaged Users. 

Thanks for posting!