In general it is very difficult to make LISTSERV throw away a message silently. One solution is to have the -request address piped to a program that looks for the fax manager's address, trashes messages coming from that address, and pipes anything else to the usual lsv_amin exit. Another is to create a special mailbox for the error messages from that list, use "Errors-To=" that mailbox, and have the discard program in its .forward. Eric