Add DMARC support

Add DMARC support

install/ubuntu/16.04/templates/dns/child-ns.tpl

@@ -9,3 +9,4 @@ ID='8' RECORD='pop' TYPE='A' PRIORITY='' VALUE='%ip%' SUSPENDED='no' TIME='%time
 ID='9' RECORD='ftp' TYPE='A' PRIORITY='' VALUE='%ip%' SUSPENDED='no' TIME='%time%' DATE='%date%'
 ID='10' RECORD='@' TYPE='MX' PRIORITY='10' VALUE='mail.%domain%.' SUSPENDED='no' TIME='%time%' DATE='%date%'
 ID='11' RECORD='@' TYPE='TXT' PRIORITY='' VALUE='"v=spf1 a mx ip4:%ip% ?all"' SUSPENDED='no' TIME='%time%' DATE='%date%'
+ID='12' RECORD='_dmarc' TYPE='TXT' PRIORITY='' VALUE='"v=DMARC1; p=none"' SUSPENDED='no' TIME='%time%' DATE='%date%'