Some mail systems generate errors in a format LISTSERV understands, some don't. If LISTSERV doesn't understand, it does nothing, because it doesn't know whether the error is permanent and who is the victim. If it understands and auto-delete is enabled, it removes the user upon a permanent error. If a user is regularly reported as nonexistent during the weekends, when he in fact does exist, he should get his technical people to fix this problem. If the post office returned all the mail you received on Mondays with a note saying you do not in fact live at that address, I'm sure you would take prompt action, and wouldn't blame the newspapers you are subscribed to for not resending every other day "just in case". But, for some reason, most people think it is ok for computers to occasionally claim that your address doesn't exist. As long as this attitude prevails, computers will continue to do that; why spend time fixing a problem if it is not perceived as a problem? Eric