title: SharePoint Designer Workflow Unable to Send Email
body: <p>I have created a sharepoint 2013 workflow in sharepoint designer. when the workflow runs it gets suspended after some time, throwing the error below:
  without sending the email. Please any help would be appreciated. I have also attached a picture to show what happens:</p>
  
  <p><a href="https://i.stack.imgur.com/T11zc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T11zc.png" alt="enter image description here"></a></p>
  
  <p>RequestorId: 494afcef-ef83-bf40-0000-000000000000. Details: An unhandled exception occurred during the execution of the workflow instance. Exception details: System.ApplicationException: HTTP 400 {"error":{"code":"-2130242040, Microsoft.SharePoint.SPException","message":{"lang":"en-US","value":"The e-mail message cannot be sent. Make sure the e-mail has a valid recipient."}}} {"Transfer-Encoding":["chunked"],"X-SharePointHealthScore":["0"],"X-SP-SERVERSTATE":["ReadOnly=0"],"DATASERVICEVERSION":["3.0"],"SPClientServiceRequestDuration":["101"],"SPRequestGuid":["494afcef-ef83-bf40-9ddb-f17a22730f4e"],"request-id":["494afcef-ef83-bf40-9ddb-f17a22730f4e"],"X-FRAME-OPTIONS":["SAMEORIGIN"],"MicrosoftSharePointTeamServices":["16.0.0.4327"],"X-Content-Type-Options":["nosniff"],"X-MS-InvokeApp":["1; RequireReadOnly"],"Cache-Control":["max-age=0, private"],"Date":["Wed, 14 Sep 2016 16:15:20 GMT"],"Server":["Microsoft-IIS/8.5"],"X-AspNet-Version":["4.0.30319"],"X-Powered-By":["ASP.NET"]} at Microsoft.Activities.Hosting.Runtime.Subroutine.SubroutineChild.Execute(CodeActivityContext context) at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager) at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation) </p>