Here's a good one.  A user correctly forwarded a confirmation back to
listserv, but his mail program put the original sender in the From:
field so listserv rejected it as being from itself.
 
To: [log in to unmask]
From: LISTSERV at SAS Institute (1.7f) <[log in to unmask]> (by way of
      [log in to unmask])
X-Sender: [log in to unmask]
Subject: Renewal of your subscription to list TSNEWS-L