domainlist local_domains = @
domainlist relay_to_domains =
-hostlist relay_from_hosts = 127.0.0.1
+hostlist relay_from_hosts = localhost
+# (We rely upon hostname resolution working for localhost, because the default
+# uncommented configuration needs to work in IPv4-only environments.)
# Most straightforward access control requirements can be obtained by
# appropriate settings of the above options. In more complicated situations,
# to any other host on the Internet. Such a setting commonly refers to a
# complete local network as well as the localhost. For example:
#
-# hostlist relay_from_hosts = 127.0.0.1 : 192.168.0.0/16
+# hostlist relay_from_hosts = <; 127.0.0.1 ; ::1 ; 192.168.0.0/16
#
# The "/16" is a bit mask (CIDR notation), not a number of hosts. Note that you
# have to include 127.0.0.1 if you want to allow processes on your host to send
# SMTP mail by using the loopback address. A number of MUAs use this method of
-# sending mail.
+# sending mail. Often, connections are made to "localhost", which might be ::1
+# on IPv6-enabled hosts. Do not forget CIDR for your IPv6 networks.
# All three of these lists may contain many different kinds of item, including
# wildcarded names, regular expressions, and file lookups. See the reference
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
+# if ipv6-enabled then instead use:
+# ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
no_more
# domains = ! +local_domains
# transport = remote_smtp
# route_data = MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
-# ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
+# ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
# no_more