Secondary Domain needs alias?

I have added a secondary domain and configured the CNAME/MX/TXT records and have all green lights on the setup screen for all 4 DNS entries. When I send email to the account on the secondary email address I get :

550 5.1.1 x@secondarydomain.net: Recipient address rejected: User unknown in virtual mailbox table

Do I need to do something to be able to add an alias of the secondary domain to a user account?

Secondary domains get their own email accounts; they do not share email (or calendar or contact) accounts in the other domains.

If you want to auto-foward, you’ll need to set up Sieve. (See other threads here about Sieve.)

I’ve put in a feature request for alias domains, where you could have a domain simply share all accounts between the domains.

Thanks, I finally saw the domain pop up on my list and was able to create a User account for it. Will check into Sieve. Thanks again.