title: How to read a federated user (from the primary domain) in B2C by email
body: <p>I have a B2C directory with local users and internal company users which are federated users (from the primary directory AAD).   </p>
  
  <p>In a custom policy I want to read either use type by email.   For local users this is not a problem. </p>
  
  <p>I have not had luck reading against the otherMails claim.  I get a validation error when uploading the policy.   I also have tried saving the user addresses to other claims (employeeId, immutableId) and attempted to read back on those but without luck.  </p>
  
  <p>Anyone else done this -- is there a different/better approach?</p>