Restricting who can send to an email address

I'd like to do so that only certain From: addresses can send to an email address (mailing list) on an Ubuntu system running Postfix. Understanding the Postfix the manuals are requires a lot of knowledge, so I'm hoping to get a complete recipe I can use. Currently this is what I have: /etc/postfix/main.cf: smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/protected_destinations smtpd_restriction_classes = insiders_only insiders_only = check_sender_access hash:/etc/postfix/insiders, reject /etc/postfix/protected_destinations: protected.list@example.com insiders_only /etc/postfix/insiders: allowed.user@example.com OK another.allowed.user@example.com OK This gives: fatal: parameter "smtpd_recipient_restrictions": specify at least one working instance of: check_relay_domains, reject_unauth_destination, reject, defer or defer_if_permit I am open to any suggestions. It doesn't have to be Postfix. It can be procmail or any other standard solution. Note: the recipient is a mailing list, and thus does not have a user account on the system account. So any solution must work without an account. ### Current mailing list implementation /etc/postfix/virtual: protected.list@example.com user1@example.com, user2.example.com, ...