title: How can I validate within an InfoPath form whether a user exists within a SharePoint Portal?
body: <p>I am creating a form within InfoPath which is to be integrated into a SharePoint 2007 Portal. Within this form there will be a textfield into which a user can enter the Name of a Person. </p>
  
  <p>How can I validate whether this Person exists or not?</p>
  
  <p>Instead of validating the user, is there a way to fill a dropdown List with <em>all</em> usernames of the portal? (which of cause would be users from the Active Directory)</p>