ensure postfix/postgrey agree on whether to communicate with ipv4 or ipv6

see https://discourse.mailinabox.email/t/postgrey-and-ipv6/227

CHANGELOG.md

@@ -13,6 +13,10 @@ Control panel:
 * Status checks would fail to load if openssh-sever was not pre-installed, but openssh-server is not required.
 * The local DNS cache is cleared before running the status checks using 'rncd' now rather than restarting 'bind9', which should be faster and wont interrupt other services.
 
+Misc:
+
+* IPv6 configuration error in postgrey.
+
 v0.05 (November 18, 2014)
 -------------------------
 

setup/mail-postfix.sh

@@ -160,6 +160,11 @@ tools/editconf.py /etc/postfix/main.cf \
 	smtpd_sender_restrictions="reject_non_fqdn_sender,reject_unknown_sender_domain,reject_rhsbl_sender dbl.spamhaus.org" \
 	smtpd_recipient_restrictions=permit_sasl_authenticated,permit_mynetworks,"reject_rbl_client zen.spamhaus.org",reject_unlisted_recipient,"check_policy_service inet:127.0.0.1:10023"
 
+# Postfix connects to Postgrey on the 127.0.0.1 interface specifically. Ensure that
+# Postgrey listens on the same interface (and not IPv6, for instance).
+tools/editconf.py /etc/default/postgrey \
+	POSTGREY_OPTS=\"--inet=127.0.0.1:10023\"
+
 # Increase the message size limit from 10MB to 128MB.
 # The same limit is specified in nginx.conf for mail submitted via webmail and Z-Push.
 tools/editconf.py /etc/postfix/main.cf \