Is it possible to make a mailman list announce only?

I've got the list reply-to address set to a specific, non-list address but if the end user chooses to reply to all, the list address gets included as well. We try to keep all subscribers set to moderated, but inevitably one or two will get through.

Can the list be set so that only messages from specified addresses get posted, regardless of moderated status?

Many thanks,

Dale