What about maintaing the subscriber data outside the list and importing it nightly in a batch job? That would override anyone unsubscribing using normal mechanisms. At most they would miss a day's worth of messages. Or if it were a critical message, import before sending. --- Spam isn't speech, just like a note wrapped around a brick thrown through a window isn't publication. William Brown Email/Internet Services Erie 1 BOCES (716)821-7285 On 5 Nov 2003, at 10:41, Paul Russell wrote: >Several entities within the University maintain lists to which subscription is, >in essence, mandatory. I have been explicitly asked whether it is technically >possible to prevent subscribers from leaving these lists. Has anyone implemented >a list exit to either prevent signoff or require owner approval for signoff?