- Plesk for Windows
- Plesk 12.5 for Linux
- Plesk Onyx for Linux
domain hosted on a Plesk server, emails sent from
are rejected with the following error:
551 This mail server requires authentication before sending mail from a locally hosted domain. Please reconfigure your mail client to authenticate before sending mail.
This error means that a server or client has connected to the SMTP service to send email, using a sender address domain which exists on the mail server, but has not authenticated.
In order to fix the issue, please, follow the steps mentioned in the KB article below: