Hi Experts,
Our emails are failing to deliver to this domain rediffmail.com with below-returning message-
f5mail-147-231.rediffmail.com rejected your message to the following email addresses:
xyz@rediffmail.com (xyz@rediffmail.com)
f5mail-147-231.rediffmail.com gave this error:
sorry, invalid HELO hostname (#5.7.1)
Please help to diagnose the issue.
Thanks, Manoj