Office Chat needs to have at least 1 domain administrator. A domain admin can be removed as an administrator by another domain admin. Here are the steps for domain admin:
1. As a domain admin, login to Admin Portal and navigate to Users tab.
2. Check the checkbox for the admin user who is to be removed as the domain admin.
3. Then, expand the “User Tools” drop-down menu and select “Remove as Administrator” option.
Once you give confirmation, the selected user becomes a non-admin user.