title: Azure AD appending '#EXT#' to UserPrincipalName
body: <p>When we create a user in Active Directory using Graph API, some characters are appended to the username (#EXT#). This makes impossible to edit the user in AD B2C's interface (<a href="https://azure.microsoft.com/en-us/documentation/articles/active-directory-b2c-limitations/" rel="nofollow noreferrer">documented problem</a>) or doing sign-in using ADAL 2.23 (Active Directory Authentication Library). </p>
  
  <p><a href="https://i.stack.imgur.com/iVZPy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iVZPy.png" alt="AD B2C interface problem"></a></p>
  
  <p>Particularly, there's an error (<code>unknown_user_type</code>) when we use <code>AcquireToken(username, password)</code> method. The error is the following:</p>
  
  <p><a href="https://i.stack.imgur.com/YdmAt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YdmAt.png" alt="ADAL error"></a></p>
  
  <p>Why is this happening? Is there any solution or workaround for this problem?. </p>
  
  <p>Regards.</p>