When a message is returned because of
an error or because a return receipt was requested, V8
sendmail adds an
Auto-Submitted: header. This header describes the
reason for the return:
Auto-Submitted: auto-generated (reason)
Auto-Submitted: auto-replied (reason) V8.12 and above
The reason can be one of four things. It can be
warning-timeout if the message has reached its
Timeout.queuewarn option threshold (Timeout). It can be
postmaster-warning if the failure was delivered to
the postmaster as a result of a problem that the postmaster should
fix, such as an MX configuration error. It can be
return-receipt if the message was returned because
of a Return-Receipt-To: header (Return-Receipt-To:) or a DSN NOTIFY=SUCCESS request (RFC1891).
Finally, it can be failure for any other reason.
In all instances, sendmail also adds a
Subject: header that contains a generic bounce
The Auto-Submitted: header should
never be defined in the configuration file.