Stop using a custom domain on iCloud.com
If you no longer want to use a custom email domain with iCloud Mail, you can remove it on iCloud.com.
When you remove a custom email domain, you can’t send or receive email for any addresses at that domain in iCloud Mail. However, any email messages you sent and received before you removed the custom domain remain in your iCloud Mail account.
Stop using a domain you own
If you stop using a domain you own that you shared with other people, they also can’t send or receive email in iCloud Mail for any addresses they created.
On iCloud.com, tap
in the toolbar, then tap Custom Email Domain.Select the domain that you want to stop using.
Scroll to the bottom, tap “Stop using this domain”, then follow the onscreen instructions.
If you’re moving your domain to a new provider, make sure to do the following:
Go to your domain registrar. Update the domain records to your new email provider and remove any iCloud related records.
Set up any email addresses you want to continue using with your new provider.
Leave a domain someone shared with you
If you leave a domain, all your email addresses are deleted. Any email messages sent to those addresses are returned to the sender.
On iCloud.com, tap
in the toolbar, then tap Custom Email Domain.Select the domain that you want to stop using.
Tap Leave Domain, then tap Leave.
When you remove a custom email domain, you can still send and receive email from your primary @icloud.com address and any iCloud Mail aliases you created.