+DEFCONF(relay_clients, <m4_dnl
+; +trusted m4_dnl
+; 172.31.80.8 m4_dnl chiark (VPN)
+; 172.29.198.161 ; 2001:ba8:1d9:a000::1:1 m4_dnl national
+)
+
+## 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/${if match_ip{$sender_host_address}{+trusted} \
+ {server}{letsencrypt}}.certlist:>):>)