How to Add a New Domain and Synchronize Users with Microsoft 365
Question details
Add a custom email domain to a local Active Directory and properly synchronize the selected users to an existing Microsoft 365 tenant.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- An organization using a local Active Directory and Azure AD Connect wants to provision a new custom domain for specific users without affecting the current Microsoft 365 environment.
- Observed behavior
- The domain must be configured both in the cloud and locally, and users must show up as 'Directory synced' under the verified domain in Microsoft 365.
Ensure you have Global Administrator privileges in the Microsoft Entra admin center and Domain Administrator rights on your local Active Directory server before making structural domain changes.
Add Custom Domain and Synchronize Active Directory Users
Use this method to establish the new domain in Microsoft 365 and configure your local Active Directory to synchronize users under the new UPN suffix.
This process involves verifying the domain in the cloud first, adding the domain as an available suffix in your local environment, updating the target users, and forcing a synchronization.
Log in to the Microsoft Entra admin center. Navigate to 'Custom domain names' and click 'Add custom domain'. Enter your new domain name, then add the provided TXT or MX records to your domain's DNS host to verify ownership.
On your local domain controller, open 'Active Directory Domains and Trusts'. Right-click 'Active Directory Domains and Trusts' in the console tree, select 'Properties', and type the new custom domain in the 'Alternative UPN suffixes' box. Click 'Add' and then 'OK'.
Open 'Active Directory Users and Computers'. Locate the users who need the new domain, right-click their account, and select 'Properties'. Under the 'Account' tab, change the UPN suffix drop-down to the newly added custom domain.
Open PowerShell as an Administrator on your Azure AD Connect server. Run the command 'Start-ADSyncSyncCycle -PolicyType Delta' to force a synchronization to Microsoft 365.
Check the Microsoft 365 admin center. Ensure the new domain is marked as 'Verified' and that the updated users appear with their new email addresses and are marked as 'Directory synced'.
Troubleshoot Missing Users During Synchronization
If some users do not appear in Microsoft 365 after the synchronization completes, follow these steps to reset their sync state.
Looking for a cost-effective alternative for your organization?
Managing complex Microsoft 365 deployments and AD synchronization requires significant IT overhead. For organizations or specific departments looking to reduce licensing costs without sacrificing daily productivity, WPS Office offers a powerful, lightweight, and completely free alternative to the Microsoft Office desktop suite.
- 1. Download WPS Office: Visit the official WPS Office website and download the free installation package for your operating system.
- 2. Install the application: Run the installer and follow the quick on-screen instructions to deploy the software on your workstation.
- 3. Open and edit files immediately: Launch WPS Office to instantly open, edit, and save your existing Microsoft Office documents without formatting loss.
Frequently Asked Questions
Can I add multiple custom domains to a single Microsoft 365 tenant?
Yes, Microsoft 365 allows you to add up to 900 custom domains to a single tenant. You simply need to verify DNS ownership for each domain in the Microsoft Entra admin center and add them as UPN suffixes in your local Active Directory.
Will adding a new domain disrupt my existing Microsoft 365 users?
No. Adding a new domain and assigning it to specific users will not affect or disrupt the accounts, emails, or services of users operating on the original domain.
How long does it take for users to sync to Microsoft 365 after making changes?
By default, Azure AD Connect runs a delta sync every 30 minutes. However, you can force immediate synchronization by running the 'Start-ADSyncSyncCycle -PolicyType Delta' PowerShell command on the AD Connect server.
Why does my verified domain say 'Setup in progress'?
This usually indicates that the DNS records (like MX or CNAME records) required for specific Microsoft 365 services (such as Exchange Online) have not fully propagated or were not added correctly. Check the DNS management page in the admin center to see which records are missing.
