[mgkimsal]

2001(?) I got an email from a client and it said "Debbie would like to revoke the earlier email". Might not have said 'revoke' but something like that. And there were a lot of extra headers I hadn't seen before. After some questioning, I got that they'd just installed some Exchange server setup (or whatever the direct predecessor was?) and you could undo email. But the 'undo' was to send an email revoking the earlier one. MAPI/internal clients understood it; to external clients like me, it was just another email. I'm not sure they (the client) quite understood that they couldn't 'undo' emails to me, because they could do it just fine to everyone else (inside the company).