The Quiet Modifier
If you add the word "quiet" to the set command, ListManager will not send a confirming message back, unless the set command fails for some reason. For instance, for a list called "jazz-discuss", you could set your membership to digest with this command:
set jazz-discuss digest quiet
Note that the "quiet" modifier is a valid argument to the unsubscribe command. The modifier must be after the list name or the email address. The modifier will prevent the Goodbye document from being sent to the unsubscriber.