-/* We use the private type T_ZNS for retrieving the nameservers for the
-enclosing zone of a domain. */
+/* We define a few private types for special DNS lookups:
+
+ . T_ZNS gets the nameservers of the enclosing zone of a domain
+
+ . T_MXH gets the MX hostnames only (without their priorities)
+
+ . T_CSA gets the domain's Client SMTP Authorization SRV record
+
+*/