title: Mailbox unavailable. The server response was: Access denied - Invalid HELO name
body: <p>i m having followingerror while sending mail with a specified domain in c# .
  Mailbox unavailable. The server response was: Access denied - Invalid HELO name (See RFC2821 4.1.1.1)</p>
  
  <p>its working perfectly while i am sending mail with gmail host.</p>
  
  <p>Thanks in advance</p>