Precedence-Mail-Headers?

I'm just wadeing through Debian-Mailinglists on the search for enhancements and false-positives.

and i just came over debian-security-announce, a lists that sends a helpful message back to submitters that aren't allowed to send out advisories.

That message didn't contain a Precedence-Header so i added one, and wondered which value would be appropriate... I remember to have seen three values: 'junk', 'bulk' and 'list' (the latter should be set for all our Mailinglists).

So i tried the usual ways to find out about some more possible values, but i couldn't find a RfC or another Document that describes correct usage of the Precedence-Header.

So, i set the Header to 'junk' now, but if someone could point me to some documentation i would be thankful.

Update: formorer pointed me to RFC 3834 - Recommendations for Automatic Responses to Electronic Mail which contains all of the things i needed to know. Thank you.