I have a distribution list that goes out to about 150 recipients that are external to our domain. Sending to this list from internal users works fine. I would like to keep these external recipients from being able to reply to messages sent to this distribution list. Is there a way to disallow replies completely? I see in the admin console where it appears I can direct replies to a specific email address. I suppose this would suffice, but I it would be nice to completely stop it. Any ideas? We are running Zimbra 8.0 on Ubuntu 12.04 LTS. Thanks.