title: Find User mailbox GUID using their email address EWS
body: <p>I am working on Outlook add-in and doing some Encryption and Decryption.  I created some hashed string on the server during POST request. That string is later passed to GET request and on the server I need to compare that hashed string to see if the user is the same user who did POST request. </p>
  
  <p>When I make a GET request I also send user smtp using <code>Office.context.mailbox.userProfile.emailAddress</code>. </p>
  
  <p><strong>Question</strong>: <em>How can find user mailboxGUID(or account information which will include mailboxGUID and more) using their email address?</em></p>