On Thu, 12 Feb 2015, Stephen J. Turnbull wrote:
Only because it already has, except for the RFC, and
http://people.dsv.su.se/~jpalme/ietf/ietf-mail-attributes.html
mentions the definition of "X-No-Archive: Yes".
Thanks. Amazing. I assumed that it had expired with Usenet.
I found it implemented in /usr/lib/mailman/Mailman/Handlers/ToArchive.py, viz. # Common practice seems to favor "X-No-Archive: yes". No other value for # this header seems to make sense, so we'll just test for it's presence. # I'm keeping "X-Archive: no" for backwards compatibility. if msg.has_key('x-no-archive') or msg.get('x-archive', '').lower() == 'no': return
http://en.wikipedia.org/wiki/X-No-Archive says "If the X-No-Archive field is set to "No", or the field is absent, a Usenet archive will not recognize a prohibition on archiving the message."
Experimentally, if I add "X-No-Archive: no" in Alpine or Thunderbird, pipermail will not archive the message, while if I add just "X-No-Archive:" to my custom headers, both programs will suppress the empty header so that mailman will archive the message.
(double negatives are confusing, I know)
I found http://kb.mozillazine.org/Custom_headers in wikipedia which explains how to add a custom header in Thunderbird, though the "easy" way seemed to not exist anymore, at least I could not find it.
GMane has a different X-Archive syntax, per http://gmane.org/expiry.php viz. X-Archive: expiry=7 http://www.mail-archive.com/faq.html specifies "X-No-Archive: yes"
I've updated the wikipedia page for fun.
-- Andrew Daviel, TRIUMF, Canada Tel. +1 (604) 222-7376 (Pacific Time)