Unable to receive an email.
Email sent from email@example.com to firstname.lastname@example.org was not delivered.
email@example.com received following message:
Technical details of permanent failure: Google tried to deliver your message, but it was rejected by the server for the recipient domain example.com by external.mailserver.com [10.10.10.10].
firstname.lastname@example.org is not configured on external mail server.
Contact owner of external mail server regarding the issue or change external mail server to local one.