HCW8001 - Issue

Hi Vitalii, 

Thank you for providing the detailed context and screenshots.  

Based on the information you've shared and additional research, I’d like to offer a few troubleshooting steps that may help address the "HCW8001 - Unable to determine the tenant routing domain" error you're encountering during the Hybrid Configuration Wizard (HCW) setup. 

Please note that as a forum moderator, I don’t have access to a full test environment, so I can’t guarantee a definitive solution. However, the following steps are commonly recommended: 

Step 1: Verify Directory Synchronization Status 

Directory synchronization must be enabled at the tenant level for the routing domain to be created automatically in Exchange Online. 

• Install the Microsoft Graph PowerShell module if not already present (run as Administrator):

    Install-Module -Name Microsoft.Graph -Scope CurrentUser
  

• Connect to Microsoft Graph (requires Global Administrator permissions; consent to scopes if prompted): 

    Connect-MgGraph -Scopes "Organization.Read.All"
  

• Check the status: 

    Get-MgOrganization | Select-Object DisplayName, OnPremisesSyncEnabled 
  

• If OnPremisesSyncEnabled is True, the feature is active—wait 5-15 minutes for any recent changes to propagate, then check accepted domains in Exchange Online (proceed to Step 2). Re-run the Hybrid Configuration Wizard (HCW). 
• If False or $null, directory synchronization isn't fully enabled. To enable it:  
  • Launch the Microsoft Entra Connect configuration wizard on your sync server. 
  • Select "Customize synchronization options" and ensure "Enable hybrid deployment" or directory synchronization is activated. 
  • Complete the wizard, trigger a full sync (via the Synchronization Service Manager or PowerShell), and wait 15-30 minutes for propagation. 

        Start-ADSyncSyncCycle -PolicyType Initial
    

  • Re-check with the Get-MgOrganization command above. Note: You cannot directly set OnPremisesSyncEnabled to $true via PowerShell; it's toggled through the Entra Connect setup process. If issues persist during enablement, this may indicate a configuration error—review Entra Connect health in the Microsoft 365 Admin Center or contact support. 

Step 2: Check Accepted Domains in Exchange Online 

• Connect to Exchange Online PowerShell: 

    Install-Module -Name ExchangeOnlineManagement Connect-ExchangeOnline 
  

(Sign in with a Global Administrator or Exchange Administrator account.) 

• List accepted domains: 

    Get-AcceptedDomain 
  

• Look for an entry like <yourdomain>.mail.onmicrosoft.com (e.g., contoso.mail.onmicrosoft.com). It should appear with DomainType set to InternalRelay or similar.  
  • If present, re-run the HCW—it should now succeed. 
  • If missing, and directory sync is enabled (from Step 1), this indicates a potential backend provisioning issue. Proceed to Step 3. 
• Additionally, confirm your primary domain (<yourdomain>) is verified and listed as an accepted domain in both the Microsoft 365 Admin Center (under Settings > Domains) and EXO PowerShell. 

Step 3: Manual Workarounds If Domain Is Still Missing 

If the routing domain doesn't appear after confirming sync is enabled and waiting: 

• Add a proxy address using the routing domain to at least one on-premises user (replace username and placeholders accordingly): 

    Set-ADUser -Identity username -Add @{ProxyAddresses="smtp:******@yourdomain.mail.onmicrosoft.com"} 
  

(Replace yourtenant with your actual tenant's name, e.g., contoso.mail.onmicrosoft.com.) Re-run the HCW. Note: This may not always work if the issue is cloud-side. 

Contact Microsoft Support 

If the above doesn't resolve the issue (e.g., domain still missing in EXO despite sync being enabled), this likely requires a backend fix on Microsoft's side, such as running provisioning scripts. In that case, I recommend opening a support ticket via the Microsoft 365 Admin Center to request a backend provisioning check. For detailed instructions on how to get help or contact support, please refer to this official guide: Get support - Microsoft 365 admin | Microsoft Learn 

I hope these steps provide helpful insight into the issue. If you have any follow-up questions, feel free to ask! 

Hi Vitalii, 

Just checking in to see if the above information was helpful.  

If you have any further updates on this issue, please feel free to post back.   

Any update would be appreciated.