Where there is a need to synchronise large user numbers into the portal the Large Tenant Mode provides a mechanism to reduce the scope of the sync process to a subset of users and can significantly improve the performance of the Sync Now process.

Large Tenant Mode is intended for user management above 1000 users, if your account has fewer then there is no need to use this function however it does support organisations with fewer users. 

Important Note:

There is an important consideration for using Large Tenant Mode that the administrator needs to be aware of.
The Sync Now function does not perform the same licence checks and validation that would otherwise take place as this is time consuming and could cause the Sync Now process to time-out in very large customer scenarios.
Using Large Tenant Mode assumes the groups being synced are properly licenced with the Phone System licence and do not have a calling plan. If this is not the case, then users will be unable to make/receive calls and existing calling plans can be disrupted.

If you wish to understand more about Azure Active Directory groups used by Large Tenant Mode, please review this article: https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/active-directory-groups-create-azure-portal

If you need more information of group-based licencing for Azure and Office 365, please see this article:

  • Basic security groups are supported with Large Tenant Mode 
  • All members of the groups chosen will be be present in the Add User list or available to be matched by the bulk import function
  • The group select option supports transitive membership, so the group can contain other groups and the service gets all of the implied users of the sub-groups.

Configuring Large Tenant Mode

Large Tenant Mode is accessed in the Teams Service tab

When you enable Large Tenant Mode (and request any subsequent changes), Microsoft will request  permission to read groups from the active directory:

Grant this permission to allow Large Tenant Mode to view the list of available directory groups 


Select the groups that contain users to be enabled on the service. Multiple groups can be added.

Review the selected groups and save the settings to complete the set-up of Large Tenant Mode

At any stage additional groups can be added using the Choose Groups link.

If you wish to remove a group, select to delete them from the list:

Take note of the warning when deleting groups as deleting a group will cause users in that group to be deleted at the next sync.