How do you allow postfix subdomain mail delivery?

I have multiple servers on my network receiving emails, and each one is set to receive messages at domain.com, mail.domain.com, and mx?.domain.com (currently running mx1 and mx2; the new ispconfig3 server is designated mx4). Server is Ubuntu, SMTP is postfix. Incoming emails generate the following log:

Note that the mailbox [email protected] has been created and will accept emails. So this is a two-part question, and I'm hoping there is an easy answer...

1. A way to tell ispconfig that emails to [email protected] will also be accepted at [email protected]
2. A method of designating that this particular server will also accept emails to all virtual domains that are tagged with this server's mx -- thus emails received for [email protected] and [email protected] would also be accepted.

Question #1 is the most important part I am focusing on, since #2 can be worked around with an easy solution to #1. I can post my config files if needed, but I don't believe this is a configuration issue. Postfix seems to be working as instructed (only allowing emails to known addresses), I just can't figure out how instruct it to allow the subdomain aliases.

 

So I'm just supposed to create a copy of every user's mailbox for every mx subdomain (and yes, there are reasons why the emails will get the mx tacked onto the address)? Assuming I were to do this, how then do you propose I get all of the received emails back into a single mailbox for the user to read?

I've been using LDAP records for years. Under postfix, I have a query that picks up associatedDomain values for each domain, then allows emails for all users under this domain to also come in under the addition domains or subdomains. I was really hoping to find something straightforward like this to easily expand on the accepted subdomains of all users under a given domain.