one of my user getting following error while sending the email on specific domain. Technical details of permanent failure: Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.7.1 Message body contains drugs online (state 17).
I have check and looks like the recipient email provider has setup Spam Filter Guard, Which is blocking specific contents of the email. Send the test message from other id it was delivered.