Adding external users to Team

Question

Hi all,

I am trying to add an external user to a team in Microsoft Teams using Microsoft Graph PowerShell with a service principal account because MFA is enforced on my tenant.

I read the following article https://learn.microsoft.com/en-us/answers/questions/76273/adding-external-users-to-teams-using-graph-api-or.html which describes that the user should first be added to Azure AD. In my scenario, that is the case.
The external user is added to Azure AD.

I use the following script to add the user to the team:

$teammailnickname = "teamname"  
$spConnection = Get-AutomationConnection -Name "AzureRunAsConnection"  
Connect-MgGraph -ClientID $spConnection.ApplicationID -TenantId "xxxxxx-xxxxxx-xxxxxx" -CertificateThumbprint $spConnection.CertificateThumbprint  
$object = Get-MgGroup -Filter "mailNickname eq '$teammailnickname'"  
$MSTeamsGroupID = $object.Id  
  
$hashGast = @{"@odata.type" = "microsoft.graph.aadUserConversationMember";"user@odata.bind" = "https://graph.microsoft.com/v1.0/users/41300318-6ec3-4142-a07f-9009e72922ac"}  
New-MgTeamMember -TeamId $MSTeamsGroupID -AdditionalProperties $hashGast -Roles "Member"  
Disconnect-MgGraph  

The following error is returned:

An unknown error has occurred.

Before MFA was enforced, I was successfully able to add external users using the Microsoft-Teams module.

Add-TeamUser -GroupId $MSTeamsGroupID -User $Gast -Role Member  

Is this unsupported through Microsoft Graph or am I missing something here?

Thanks for all help provided.
BR,
Joost

Answer 1

Answer from Microsoft Support:

The API that you are using does not allow for adding guest users in this way Update document to state that guest members cannot be added to a team with app permissions · Issue #11757 · microsoftgraph/microsoft-graph-docs · GitHub -> https://github.com/microsoftgraph/microsoft-graph-docs/issues/11757

You will need to add the member using the Group API instead, and the cmdlet respective to the API will be New-MgGroupMember (Microsoft.Graph.Groups) | Microsoft Learn -> https://learn.microsoft.com/en-us/powershell/module/microsoft.graph.groups/new-mggroupmember?view=graph-powershell-beta

The only caveat is that the guest users will get a Teams notification saying that "Unknown has added you to a Team". Also, for a user to sync from a Group to a Team, it can take up to 48 hours.

Answer 2

@Joost van der Linden -- I just wanted to let you know that I ran into this same issue while using the REST API. As a workaround, I tried using the "Add members in bulk" endpoint with just one External/Guest user and it worked for me.