SharePoint 2013 - Workflow suspenso: System.ApplicationException: HTTP 401

O fluxo de trabalho no SharePoint 2013 fica normalmente no estado suspenso com a mensagem de erro "System.ApplicationException: HTTP 401" se o fluxo está configurado para enviar e-mail(s) para um grupo do SharePoint que não permite a exibição da associações.

Mensagem de erro no interface:

RequestorId: <GUID>. Details: An unhandled exception occurred during the execution of the workflow instance. Exception details: System.ApplicationException: HTTP 401 {"Transfer-Encoding":["chunked"],"X-SharePointHealthScore":["0"],"SPRequestGuid":["<GUID>"],"request-id":["<GUID>"],"X-FRAME-OPTIONS":["SAMEORIGIN"],"MicrosoftSharePointTeamServices":["15.0.0.4569"],"X-Content-Type-Options":["nosniff"],"X-MS-InvokeApp":["1; RequireReadOnly"],"Cache-Control":["max-age=0, private"],"Date":["Tue, 15 Oct 2014 14:24:05 GMT"],"Server":["Microsoft-IIS\/8.5"],"WWW-Authenticate":["NTLM"],"X-AspNet-Version":["4.0.30319"],"X-Powered-By":["ASP.NET"]}

Mensagem de error nos logs do SharePoint:

Exception occured in scope Microsoft.SharePoint.Utilities.SPUtility.SendEmail. Exception=System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))     at Microsoft.SharePoint.SPGlobal.HandleUnauthorizedAccessException(UnauthorizedAccessException ex)     at Microsoft.SharePoint.Library.SPRequest.GetUsersDataAsSafeArray(String bstrUrl, UInt32 dwUsersScope, UInt32 dwUserCollectionFlags, String bstrValue, UInt32 dwValue, UInt32& pdwColCount, UInt32& pdwRowCount, Object& pvarDataSet)     at Microsoft.SharePoint.SPUserCollection.InitUsersCore(Boolean fCustomUsers, String[] strIdentifiers, SPUserCollectionFlags ucf)     at Microsoft.SharePoint.SPBaseCollection.GetEnumerator()     at Microsoft.SharePoint.Utilities.SPUtility.ResolveAddressesForEmail(SPWeb web, IEnumerable`1 addresses, AddressReader func)     at Microsoft.SharePoint.Utilities.SPUtility.SendEmail_Client(EmailProperties properties)     at Microsoft.SharePoint.ServerStub.Utilities.SPUtilityServerStub.InvokeStaticMethod(String methodName, ClientValueCollection xmlargs, ProxyContext proxyContext, Boolean& isVoid)     at Microsoft.SharePoint.Client.ServerStub.InvokeStaticMethodWithMonitoredScope(String methodName, ClientValueCollection args, ProxyContext proxyContext, Boolean& isVoid)

Solução: Permitir a exibição das associações para todos os usuários do SharePoint ou utilizar um outro grupo.

Fontes:

HTTP Unauthorized to /_vti_bin/client.svc/sp.utilities.utility.SendEmail

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