+## 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:>):>)
+