Office 365 Object Limit

Your default directory service quota is calculated according to the following guidelines:

• If you don't have any verified domains
  
  The current directory service quota in Azure AD is 50,000 objects.
  • If your organization was created before October 5, 2011, your default directory service quota is 10,000 objects.
  • If your organization was created after October 5, 2011 and before May 2012, your default directory service quota is 20,000 objects.
  • If your organization was created after May 2012, your default directory service quota is 50,000 objects.
• If you have at least one verified domain
  The default directory service quota in Azure AD is 300,000 objects
• If you have more than 300,000 objects in your on-premises Active Directory directory service, to increase the number of objects that can be synced beyond 300,000, contact Support.