I encountered this error when I added a check_sender_access clause to my smtpd_recipient_restrictions in postfixes "main.cf":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 haven't really checked, but I am guessing this is because smtpd_recipient_restrictions as the last clause isn't specifically rejecting all mails that aren't wanted, and