title: Mailbox unavailable. The server response was: bosauthsmtp05: Host 117.58.242.18: No unauthenticated relaying permitted
body: <p>An exception of type 'System.Net.Mail.SmtpException' occurred in System.dll but was not handled in user code
  <a href="https://i.stack.imgur.com/Ava9W.png" rel="nofollow noreferrer">enter image description here</a>
  Additional information: Mailbox unavailable. The server response was: bosauthsmtp05: Host 117.58.242.18: No unauthenticated relaying permitted</p>