Warning Messages (warnpost, nowarnpost, copywarnpost, errwarnpost)

In addition to returning messages, IMTA sometimes sends warnings detailing messages that it has been unable to deliver. This is generally due to timeouts based on the setting of the notices channel keyword, although in some cases channel programs may produce warning messages after failed delivery attempts. The warning messages contain a description of what's wrong and how long delivery attempts will continue. In most cases they also contain the headers and the first few lines of the message in question.

Optionally, a copy of all warning messages is sent to the local postmaster. This can be somewhat useful for monitoring the state of the various queues, although it does result in lots of traffic for the postmaster to deal with. The keywords warnpost, copywarnpost, errwarnpost, and nowarnpost are used to control the sending of warning messages to the postmaster.

warnpost-Tells IMTA to send a copy of all warning messages to the postmaster unconditionally

copywarnpost-Instructs IMTA to send a copy of the warning to the postmaster, unless the originator address on the undelivered message is blank.

errwarnpost-Instructs IMTA to send only a copy of the warning to the postmaster when the notice cannot be returned to the originator.

No warning messages are ever sent to the postmaster if nowarnpost is specified. The default, if none of these keywords is specified, is to send a copy of warnings to the postmaster unless warnings are completely suppressed with a blank Warnings-to: header or a blank envelope From: address. This default behavior does not correspond to any of the keyword settings.