If an update caused the issue:
If the file is missing, that is your cause. If an update caused the issue: If the
If you edited sasl_passwd or transport maps, you must run postmap /etc/postfix/filename and then postfix reload for the changes to take effect. If an update caused the issue: If the
The Postfix error message typically occurs when the mail queue manager cannot find a valid delivery agent (transport) for a specific email's destination . This often follows a previous critical failure that caused the queue manager to throttle or "suspend" further delivery attempts to that destination. Core Causes If an update caused the issue: If the