Never mind, I found the answer.
Majordomo (user 'majordom') needs to be set up as a truested user in the
sendmail config file; otherwise sendmail will warn that a non-trusted
user is altering the "From" header in a mail message.
On Thu, 19 Dec 1996, Bill wrote:
> When Majordomo re-sends mail messages to the list members through
> sendmail (my mail server), sendmail includes an
> "X-Authentication-Warning" header in the message, presumably to warn that
> the real sender of the message is not who is stated in the new "From"
> Have others been experiencing this? Is there a way to tell sendmail not
> to include the authentication warning? This extra header, although
> useful in most situations, is confusing some of the list members.
> Thanks for your help.
> - Bill.