Index: conf/main.cf
--- conf/main.cf.orig
+++ conf/main.cf
@@ -137,6 +137,9 @@ mail_owner = postfix
 #inet_interfaces = $myhostname
 #inet_interfaces = $myhostname, localhost
 
+# OpenBSD is IPv6-capable - use all available address families.
+inet_protocols = all
+
 # The proxy_interfaces parameter specifies the network interface
 # addresses that this mail system receives mail on by way of a
 # proxy or network address translation unit. This setting extends
@@ -682,4 +685,3 @@ sample_directory =
 # readme_directory: The location of the Postfix README files.
 #
 readme_directory =
-inet_protocols = ipv4