If you are experiencing an issue where mail sent to a particular domain using Postfix is looping back to yourself, it could be due to a problem with the domain's DNS configuration or with the Postfix configuration.
Here are some possible solutions to this issue:
Check the DNS configuration for the domain and make sure that it is correct and up-to-date. The DNS records for the domain should include an MX record that points to the correct mail server for the domain.
Check the Postfix configuration to make sure that the mydestination parameter in the main.cf configuration file does not include the domain in question. The mydestination parameter specifies the domains that the Postfix server will accept mail for, and if the domain is listed in this parameter, it may cause the mail to loop back to the server.
Check the Postfix configuration to make sure that the virtual_alias_maps parameter in the main.cf configuration file is correctly configured. The virtual_alias_maps parameter specifies the aliases that the Postfix server will use to redirect mail to other destinations. If there is a problem with the virtual_alias_maps configuration, it could cause the mail to loop back to the server.
Check the Postfix logs for any error messages or clues that may help to identify the cause of the issue. The Postfix logs are usually located in the /var/log/maillog file or in the syslog facility.
If none of these solutions resolves the issue, you may need to consult the Postfix documentation and online resources for further troubleshooting guidance. It's important to note that troubleshooting issues with Postfix can be complex and may require a good understanding of the Postfix configuration and the underlying system.