So, Auto-Submitted really isn't a good field to use for loop control.
I concur. Also, as a "notification" is a different best from an "auto
response", so use of auto-submitted seems a bit wrong.
It seems appropriate to use another mechanism for notification loop
detection.
From RFC 3834:
The purpose of the Auto-Submitted header field is to indicate that
the message was originated by an automatic process, or an automatic
responder, rather than by a human; and to facilitate automatic
filtering of messages from signal paths for which automatically
generated messages and automatic responses are not desirable.
Notifications originate by an automatic process, not by a human. We
use this field as intended.
One can argue about using it for loop control. If somebody is on
vacation, his Sieve script will not respond to automatically generated
alarms and the role account used as sender of these alarms is not
notified about the recipient being away, despite expecting them, as he
would get notified if the recipient mailbox overflowed. We decided loop
control using widely implemented mechanisms is more important than minor
gripes about missing responses for "vacation". To me, the same reason
applies here.
Michael