if a custom CNAME record is set, don't add a default A/AAAA record, e.g. for 'www'

see https://discourse.mailinabox.email/t/multiple-domains-in-mail-in-a-box-with-the-domains-being-hosted-elsewhere/56/18

CHANGELOG.md

 CHANGELOG
 =========
 
+Development
+-----------
+
+DNS:
+
+* If a custom CNAME record is set, don't add a default A/AAAA record, e.g. for 'www', which end up preventing the CNAME record from working.
+
 v0.06 (January 4, 2015)
 -----------------------
 

management/dns_update.py

@@ -212,6 +212,7 @@ def build_zone(domain, all_domains, additional_records, env, is_zone=True):
 		records.append((qname, rtype, value, "(Set by user.)"))
 
 	# Add defaults if not overridden by the user's custom settings (and not otherwise configured).
+	# Any "CNAME" record on the qname overrides A and AAAA.
 	defaults = [
 		(None,  "A",    env["PUBLIC_IP"],       "Required. May have a different value. Sets the IP address that %s resolves to for web hosting and other services besides mail. The A record must be present but its value does not affect mail delivery." % domain),
 		("www", "A",    env["PUBLIC_IP"],       "Optional. Sets the IP address that www.%s resolves to, e.g. for web hosting." % domain),
@@ -221,7 +222,7 @@ def build_zone(domain, all_domains, additional_records, env, is_zone=True):
 	for qname, rtype, value, explanation in defaults:
 		if value is None or value.strip() == "": continue # skip IPV6 if not set
 		if not is_zone and qname == "www": continue # don't create any default 'www' subdomains on what are themselves subdomains
-		if not has_rec(qname, rtype):
+		if not has_rec(qname, rtype) and not has_rec(qname, "CNAME"):
 			records.append((qname, rtype, value, explanation))
 
 	# Append the DKIM TXT record to the zone as generated by OpenDKIM.