Could not resolve user ....

Question

When I try to add one external user to my sharepoint site ,system reminds that "could not resolve user xxxxxx@xxxxx.

I had added the external domain in on Cross-tenant access settings and External collaboration settings

Answer 1

Hi @Teams administrator, 

Based on your description, this error usually means SharePoint is still unable to resolve that guest at the SharePoint sharing layer, even if the external domain has already been added in cross-tenant access and external collaboration settings. 

Please kindly check the following configurations: 

1. SharePoint tenant and site sharing settings 
   • When external sharing is turned off for the entire SharePoint environment, you will not be able to turn it on for specific site collections. 
   • Therefore, in SharePoint admin center, confirm external sharing is enabled for the tenant first, then verify the specific site also allows external sharing. 
   • 
2. Whether SharePoint/OneDrive integration with Microsoft Entra B2B is enabled 
   • Entra external collaboration settings are not always applied to SharePoint/OneDrive unless this integration is enabled. 
   • Please refer to the article to verify whether this feature is enabled: Microsoft Entra B2B integration for SharePoint & OneDrive - SharePoint in Microsoft 365 | Microsoft… 
3. People picker / guest lookup behavior  Searching existing guest users in the SharePoint people picker can be off by default, which may cause guest lookup issues even when the guest already exists. 
4. Scope of the issue  Please test whether this happens:  
   • only with this one external user, 
   • with other external users also, 
   • or only on this one site. 
5. Remove and re-invite the guest if needed  If there may be a stale or incomplete invitation, try withdrawing the pending invitation (if not yet accepted), or remove the guest access and invite them again.

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If the issue still continues after the checks above, I would kindly suggest that your Microsoft 365 or SharePoint admin open a support ticket in the Microsoft 365 admin center. This type of issue can be complex to verify and configure because it may involve multiple layers such as SharePoint sharing settings, guest invitation status, tenant configuration, and backend guest resolution behavior.  

Microsoft Support agent has the required permissions and tools to review the tenant-side configuration directly, connect remotely if needed, and collect additional diagnostics such as logs for deeper investigation. 

• For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin.  
• In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support.  

I hope it clears your concerns, should you have any further questions, please feel free to reach out.

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Answer 2

The external user cannot be resolved because the guest account is not properly provisioned in Microsoft Entra ID (Azure AD) for the tenant, even though cross-tenant and external collaboration settings are configured.

Use these steps to fix it:

1. Make sure the guest account actually exists in the directory
   • If the user has never been invited before, explicitly invite the user as a guest into the tenant (for example, via Azure AD → Users → New guest user, or via a normal SharePoint sharing invitation and having them complete the invitation process).
   • If Conditional Access is used (for example, requiring MFA or Terms of Use), the guest must be fully provisioned in Entra ID before SharePoint can honor the permissions. Otherwise, the account will not be found and cannot be resolved.
2. If the guest was invited before but is in a bad state, remove and re‑invite
   • Use Microsoft Graph PowerShell to remove the problematic guest and then invite again:
     1. Install the module:

                Install-Module Microsoft.Graph -Scope CurrentUser -Repository PSGallery
        

     2. Connect with sufficient directory permissions:

                Connect-MgGraph -Scopes "User.ReadWrite.All","Directory.ReadWrite.All"
        

     3. Find the guest by UPN (replace with the actual guest UPN in the tenant):

                $guestUpn = 'jondoe_contoso.com#EXT#@yourdomain.onmicrosoft.com'
                Get-MgUser -Filter "UserPrincipalName eq '$guestUpn'" -Property Id,UserPrincipalName,UserType | Format-Table -AutoSize
        

     4. Soft‑delete the guest:

                Remove-MgUser -UserId <user-id> -Confirm:$false
        

     5. (Optional) Permanently delete from the recycle bin:

                $deleted = Get-MgDirectoryDeletedItem -Filter "Id eq '<user-id>'" -All
                Remove-MgDirectoryDeletedItem -DirectoryObjectId $deleted.Id -Confirm:$false
        

   • After removal, send a fresh SharePoint sharing invitation to the external email address and have the user accept it with the same account.
3. Clear browser cache on the admin side
   • SharePoint People Picker caches user entries. After removing/re‑inviting the guest, clear browser cache including cookies and website data, then try resolving the user again when assigning permissions.
4. Ensure B2B integration is enabled if Conditional Access is in use
   • If Conditional Access policies are applied to guests, enable SharePoint integration with Microsoft Entra B2B so that sharing uses Azure B2B Invitation Manager and properly provisions guest accounts. Otherwise, the guest may not be created in Entra ID and cannot be resolved.

If, after these steps, the user still cannot be resolved, verify with the Entra admin that the guest object exists and is not blocked by cross‑tenant or Conditional Access policies.

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References:

• Error "Selected user account does not exist" when new guests access a SharePoint resource
• Error when a guest user accepts a SharePoint Online invitation by using another account
• Manage cross-tenant access settings for B2B collaboration
• Cannot add external users to a SharePoint Online External Content Type in the SharePoint admin center