The “mail for domain.com loops back to myself” error occurs when a mail server is configured to accept email for a domain it is responsible for but is unable to deliver it to the correct recipient. This usually happens because the DNS MX record for the domain points to the server itself.
To fix this error, you need to check the DNS MX record for the domain and make sure it points to the correct server. You can use the dig command to check the MX record:
dig domain.com MX
This command will display the MX record for the domain. If it points to the same server that is reporting the error, you need to update the MX record to point to the correct server.
Once you have updated the MX record, you need to reload the DNS cache on the server so that it can pick up the changes. This can be done by running the following command:
sudo /etc/init.d/nscd restart
Finally, restart the Postfix service to ensure that the changes are applied:
sudo service postfix restart
This should fix the “mail for domain.com loops back to myself” error in Postfix.