title: Exchange 2010, Cannot ADD new user to Delivery Option, Set-Mailbox Failed, Error: Couldn't find object, Send on Behalf, isn't the expected type
body: <p><strong><em>Aim:</em></strong></p>
  
  <ul>
  <li>Try to add new user to "Delivery Options -> Send on Behalf -> Grant this permission to:".</li>
  <li>This is found in:</li>
  </ul>
  
  <blockquote>
    <p>Mailbox -> Properties -> Mail Flow Settings -> Delivery Options</p>
  </blockquote>
  
  <p><strong><em>Issue:</em></strong></p>
  
  <ul>
  <li>Failed to add new user to "Delivery Options"</li>
  <li>Got error message</li>
  </ul>
  
  <blockquote>
    <p>Error: Couldn't find object "DOMAINxxxx/OUxxxx/USERxxxx". Please make
    sure that it was spelled correctly or specify a different object.
    Reason: The recipient DOMAINxxxx/OUxxxx/USERxxxx isn't the expected
    type.</p>
  </blockquote>
  
  <ul>
  <li>But <strong>USERxxxx</strong> is <strong>NOT</strong> in the list of "Grant this permission
  to"</li>
  <li>Also <strong>USERxxxx</strong> is has already been <strong>DISABLED</strong> in Active Directory</li>
  </ul>
  
  <p><strong><em>Attempted Fix:</em></strong></p>
  
  <ul>
  <li>Confirmed <strong>PublicDelegates</strong> is set to <strong>"not set"</strong></li>
  </ul>
  
  <blockquote>
    <p>ADSI edit -> USERxxxx -> Properties -> PublicDelegates</p>
  </blockquote>
  
  <ul>
  <li>Re-enabled <strong>USERxxxx</strong> account in <strong>Active Directory</strong> and then tried to ADD new user, still <strong>FAILED</strong></li>
  </ul>
  
  <p><strong><em>Current Fix Result:</em></strong></p>
  
  <ul>
  <li>Exchange <strong>FAILED</strong> to add new user to "Delivery Options" even the "PublicDelegates" has no value in "ADSI edit"
  <br><br></li>
  </ul>
  
  <p><strong><em>Reference Picture of the issue:</em></strong>
  <img src="https://i.stack.imgur.com/bT70P.jpg" alt="enter image description here"></p>