+
+ # Determine which domains are "left over" for this plugin. A domain
+ # is considered "left over" if it has been removed from Postfixadmin
+ # but not some other plugin.
+ #
+ # The leftovers are determined with respect to the list *db_domains*
+ # of domains that Postfixadmin knows about.
+ #
+ # @param db_domains [Array<Domain>] a list of domains that are present
+ # in the Postfixadmin database.
+ #
+ # @return [Array<Domain>] a list of domains known to this plugin but
+ # not to Postfixadmin.
+ #