This implies the exchange has error. It is a permanent error and the server would not attempt to send the message once more.


Related to the sending mail server is being blacklisted and it think the email is a spam.


Step 1: Check Your Spam Records

Check cautiously on the off chance that you wound up in spam records, or depend on an expert SMTP administration like turboSMTP that will invalidate this issue.

Step 2: Try Again

Check the email address ensure it is a valid and not being blacklisted and try again.