: Postfix requires strict ownership (usually root or postfix ) and permissions for its spool directories, sockets, and configuration files. Incorrect permissions can prevent the queue manager from communicating with the delivery agents.
The key word in this error is temporarily . Unlike a fatal bounce (which sends a failure report to the sender), a temporary suspension tells Postfix to queue the message and try again later. This is typically governed by the minimal_backoff_time and maximal_backoff_time parameters. The phrase "unknown mail transport error" is Postfix’s default fallback when a lower-level component (like the local delivery agent local , the virtual agent virtual , or a pipe to a content filter) returns an exit code or signal that does not map to a specific known error (e.g., "permission denied" or "disk full"). : Postfix requires strict ownership (usually root or
: Run df -h to ensure you haven't run out of space on the /var or root partition. Unlike a fatal bounce (which sends a failure