+queue_run_in_order
+
+# ----- Routers -----
+
+begin routers
+
+client:
+ driver = accept
+ condition = ${if eq {SERVER}{server}{no}{yes}}
+ transport = send_to_server
+
+server:
+ driver = accept
+ transport = send_to_server
+
+
+# ----- Transports -----
+
+begin transports
+
+send_to_server:
+ driver = smtp
+ connection_max_messages = 0
+ allow_localhost
+ hosts = 127.0.0.1
+ port = PORT_D
+ hosts_try_fastopen = :
+ # assumes that HOSTIPV4 can send to 127.0.0.1
+ interface = ${if eq {$sender_address_domain}{dustybelt.tld} {127.0.0.1}{HOSTIPV4}}
+
+# ----- Retry -----
+
+begin retry
+
+* * F,5d,10s