Introduce rough docker support

pillar.example

@@ -3,3 +3,4 @@ postfix:
     message_size_limit: '10240000'
     relayhost: 'smtp.example.com'
     rootmail-destination: 'rootmails@example.com'
+    docker-support: False

postfix/nullclient/etc/postfix/main.cf

@@ -36,11 +36,11 @@ local_recipient_maps = unix:passwd.byname
 
 mydestination = {{ minion_id }}, localhost
 relayhost = {{ pillar['relayhost'] }}
-mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
+mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 {% if pillar['docker-support'] %}172.16.0.0/12{% endif %}
 mailbox_command = procmail -a "$EXTENSION"
 mailbox_size_limit = 0
 recipient_delimiter = +
-inet_interfaces = 127.0.0.1
+inet_interfaces = 127.0.0.1{% if pillar['docker-support'] %}, 172.17.0.1{% endif %}
 
 # Allow local rewriting for (local user) sender addresses
 sender_canonical_maps = hash:/etc/postfix/sender_canonical_maps