I once in a while get list mail bounced back to me as a
warning that it hasn't been delevered for "N hours," N usually being
4, 8 or 12.  I recently got the following advice, purporting to be
effective in reducing some of the warning messages at least:
 
> I encourage you to add a "Precedence: list" envelope header to your
> mailings.  Sendmail-8.6.x does not send delivery warning messages to
> messages with this header line.  Many sites run sendmail, and you
> undoubtedly get numberous of these warning messages.  These warning
> messages are generated automatically when a machine is down for more
> then 8 hours (in this case), but do not indicate a bad email address.
 
        Now, I want to try this out, but I can't figure out how I am
supposed to add a "Precedence: list" header line (if that's what I'm
supposed to do) to all outgoing list mail.  I will appreciate all
advice about this matter.  Thanks,
 
        Taner Edis,  SKEPTIC list owner