initial change for mta-sts support in mailinabox

conf/mta-sts.txt

@@ -0,0 +1,4 @@
+version: STSv1
+mode: testing
+mx: PRIMARY_HOSTNAME
+max_age: 86400

conf/nginx-alldomains.conf

@@ -21,6 +21,9 @@
 	location = /mail/config-v1.1.xml {
 		alias /var/lib/mailinabox/mozilla-autoconfig.xml;
 	}
+	location = /.well-known/mta-sts.txt {
+		alias /var/lib/mailinabox/mta-sts.txt;
+	}
 
 	# Roundcube Webmail configuration.
 	rewrite ^/mail$ /mail/ redirect;