LISTSERV doesn't care about the 'Errors-To:' header, which by the way is a sendmailism, and the duplicate warning is by no means a delivery error. It does not follow the same rules as delivery errors, which are sent to the list owner and not the original poster. The duplicate may not be due to a network glitch, there are cases where people legitimately need to post exactly the same thing at regular intervals, and without the warning they might never know that their message is not getting through. Eric