iRedAdmin-Pro-1.3.0 now supports domain alias.
What "Domain Alias" is
Domain alias allows you to bind as many domains as you want to one domain, all emails sent to alias domain "user@aliasDomain.com" will be delivered to account under your primary domain "user@example.com" (same username, different domain part in email address). you don't need to manage accounts for bound domain "aliasDomain.com".
You can simply manage alias domains in domain profile page, alias as many as you want. Is it simple and clear enough?