Domain Cannot Be Synchronized due to Large Number of Users (code 3529)

Situation

A domain synchronization failed with the following warning message:

The M365/Google Backup system cannot automatically add such a large number of users at once. Please contact the support team for assistance (Code: 3529)

Only users already added to the backup are synchronized.

Cause

By design, the Microsoft 365/Google Workspace Backup system cannot automatically add more than 20,000 users at once.

Solution

You should contact the support team to request permission for a full domain sync, allowing all users to be backed up. Only users already added to the backup will be synchronized until this permission is granted.