title: Leading underscores in an email address?
body: <p>What RFC would I refer to in order to find out if a leading underscore in the local part of an email address is acceptable?</p>
  
  <p>Example: <code>_johndoe@hotmail.com</code></p>
  
  <p>Of course, this question can also apply to any leading special character.</p>
  
  <p>I found this line in Wikipedia, but couldn't find any reference within the RFC itself. Did I miss something here?</p>
  
  <p><em>Local part
  The local-part of the email address may use any of these ASCII characters RFC 5322 Section 3.2.3:</em></p>