How to set new domain as default domain for mail server

How to set new domain as default domain for mail server

Hi,
 
We recently acquire a new domain that we want to be our default domain. I mean we setup business (and all Zoho services) with www.olddomain.com; now we want to access trought www.newdomain.com.
 
I added, validated and set as primary domain www.newdomain.com
I created MX records and activate mail service for www.newdomain.com
I added new mail aliases for all users name@newdomain.com. and set as default mail account
 
Now, for any user we can see the @newdomain.com account (Inbox, Trash, ...). Still appears @olddomain.com. I need to setup newdomain accounts because we need to deactivate mail server for olddomain.com
 
Thanks,
Javier