If you remove a domain from your Google Apps account, Google Apps no longer accepts email addressed to any users in that domain. In fact, you must remove all Google Apps user accounts, email aliases (nicknames), and groups from a domain before you can remove the domain. (You can use the Search accounts box at the top of the Admin console to confirm that the domain doesn't include any users, aliases, or groups.) You do not need to remove user accounts from a domain alias in order to delete it.

Before removing the domain from your account, we recommend that you update the domain's MX records so that they do not point to the Google Apps mail servers. If you do not, all messages addressed to users in the domain will be bounced back to the sender. You cannot create user accounts or email aliases in the domain once you remove it from the Google Apps account.

To remove a domain from your Google Apps account:

1. Sign in to the Google Admin console. 
   
   
2. Do one of the following:
   • In the classic Admin console, click Domain settings > Domain names.
   • In the new Admin console, click Domains.
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3. Click Remove in the row for the domain.
   
   
4. Click Yes, remove domain to confirm that you wish to remove the domain from your Google Apps account.
   
   If there are still users with email addresses in this domain, an error message appears and the domain is not removed.