After sending an email from one domain to another (both hosted on the same Plesk server), the email is not delivered and a bounce message is received:
Delivery to the following recipient failed permanently:
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 mail.example.com [203.0.113.2].
An error occurred while sending mail.
550 Requested action not taken: mailbox unavailable or not local
Please check the message recipient [email protected] and try again.
Mail for the recipient domain is served externally (for example, at Gmail or Office 365).
Mail service of the recipient domain is enabled in Plesk/MailEnable.
Disable mail service for the domain, mail of which is served externally, in Plesk at Domains > example.com > Mail tab > Mail Settings.