+DEFCONF(relay_clients, <m4_dnl
+; +allnets m4_dnl
+; 172.31.80.8 m4_dnl chiark (VPN)
+)
+
+## DKIM headers list.
+## Surprise! Internal whitespace isn't allowed here.
+DEFCONF(dkim_headers, m4_dnl
+References : In-Reply-To : Subject : To : Date : Message-ID : m4_dnl
+From : Sender : Reply-To : Cc : m4_dnl
+Content-Transfer-Encoding : Content-Type : MIME-Version : m4_dnl
+Content-ID : Content-Description m4_dnl
+)
+
+## TLS certificate list.
+DEFCONF(certlist,
+<:m4_ifelse(t, m4_ifelse(MODE, hub, nil, MODE, srv, nil, t),
+<:CONF_sysconf_dir/server.certlist:>,
+<:CONF_sysconf_dir/${if ={$received_port}{CONF_submission_port}{server}\
+ {${if match_ip{$sender_host_address}{+trusted} \
+ {server}{letsencrypt}}}}.certlist:>):>)