Delivery Temporarily Suspended Unknown Mail: Transport Error Postfix Upd

The error "unknown mail transport error" is a generic wrapper indicating that the process responsible for delivering mail (typically smtp or lmtp ) failed unexpectedly or could not be initialized.

This message is a digital warning light. It tells you something is wrong, but it doesn’t tell you what. The word "unknown" is particularly alarming because it suggests Postfix itself cannot categorize the nature of the failure. The error "unknown mail transport error" is a

Examine your Postfix master.cf transport: your lookup tables (e.g.

Temporarily test with SELinux in permissive mode: The error "unknown mail transport error" is a

Following a system or Postfix update, your lookup tables (e.g., sasl_passwd ) might need to be re-indexed using the newaliases Virtualmin Community How to Troubleshoot Check the Real Error Logs