I found this in the findmail FAQ. I wonder if it's common enough
to be included into mhonarcs TODO list :-)
'Twould be nice. I do this kind of thing already, but most of the
people who use the list aren't too sure what a header even is. I
also check to see if the last line of a message contains the
phrase "no archive" -- this way .sig files can always incorporate
the necessary instructions to prevent archiving.
So besides 'X-No-archive: yes' and 'Restrict: no-external-archive'
headers, I feel that it would be useful to add checks for patterns
within a specified portion of a message's body. Maybe I'll work on
4. As a list contributor, I do not want my messages archived.
Before you send your message, please place 'X-No-Archive: yes' in the
header of your email message ( see DejaNews). We will be looking for
this and not archive any messages with this header (we also support the
'Restrict: no-external-archive' header.)
Subject: I have this great new idea
I have this great new idea for...
Most mail programs allow you to add this header line simply by making
it the first line in the message portion. The message recipients will see
the header line in the header rather than as part of the message. Do not
put it in the "Subject:" header line, however, as this will not work.