exchangewebservices - ExchangeImpersonation SOAP header must be present for this type of oauth token accessing shared mailbox

Question

With recent changes in Exchange web services where basic authentication will be discontinued in Office 365, I'm switching my code to Oauth.

Everything is working fine except when I'm accessing a shared mailbox or Unified group. By experience, In basic auth, I must not set the ImpersonatedUserId.

with Oauth:

• If I don't set this header, I receive an error saying "ExchangeImpersonation SOAP header must be present for this type of oauth token".
• If I set this header, I receive an error saying "The SMTP address has no mailbox associated with it."

The mailbox exists AND I access it using basic authentication.

The problem is the following: how to programmatically access a sharedmailbox (or Unified group mailbox) using oauth

Oauth setup : App Permission correctly set (If I access a user mailbox programmatically it works, If I access a shared mailbox, it doens not)

Code to generate token

_service = new ExchangeService(ExchangeVersion.Exchange2013);
_service.TraceFlags = TraceFlags.None;
_service.PreAuthenticate = true;
_service.Timeout = 600000; // 10 minutes
string token = GetTokenForUserAsync().Result;
_service.Credentials = new OAuthCredentials(token);   
_service.UseDefaultCredentials = false;
string url = "https://outlook.office365.com/ews/Exchange.asmx";
_service.Url = new Uri(url);
_service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, "sharedmailbox@domain.com");

_fdInbox = Microsoft.Exchange.WebServices.Data.Folder.Bind(_service, new FolderId(WellKnownFolderName.Inbox, "sharedmailbox@domain.com"));


private async System.Threading.Tasks.Task<string> GetTokenForUserAsync()
    {
        string domainName = _context.MigrationDefinition.TargetConfiguration.DomainName;
        string clientId = _context.MigrationDefinition.TargetConfiguration.ClientID;
        string clientSecret = _context.MigrationDefinition.TargetConfiguration.ClientSecret;
        string microsoftLoginUrl = AzureURL.GetLoginUrl(_context.MigrationDefinition.TargetConfiguration.ServerRegion);
        string loginUrl = string.Format("{0}/{1}", microsoftLoginUrl, domainName);
        loginUrl = "https://login.microsoftonline.com/" + domainName + "/oauth2/v2.0/token";
        string redirectUri = "https://myapp.azurewebsites.net";
        IConfidentialClientApplication app = ConfidentialClientApplicationBuilder.Create(clientId)
            .WithClientSecret(clientSecret)
            .WithAuthority(loginUrl)
            .WithRedirectUri(redirectUri)
            .Build();

        var ewsScopes = new string[] { "https://outlook.office365.com/.default" };
       
        Microsoft.Identity.Client.AuthenticationResult result = await app.AcquireTokenForClient(ewsScopes).ExecuteAsync();
        return result.AccessToken;
    }

question from:https://stackoverflow.com/questions/65938777/exchangeimpersonation-soap-header-must-be-present-for-this-type-of-oauth-token-a

Answer 1

Waitting for answers