When you subscribe to iCloud+, you can add up to five custom email domains and create email addresses for those domains on your iPad. You can then send and receive mail in the Mail app
You can add a custom email domain you already own to iCloud Mail, or buy a new one.
Note: You need to have a primary iCloud Mail address before you can add a custom email domain on iPad. See Import existing email messages to your custom iCloud Mail address in the iCloud User Guide.
After you add a custom domain name, you can easily create and delete email addresses for that domain.
Go to Settings > [your name] > iCloud > Mail (under Saved to iCloud).
Tap Custom Email Domain, then tap your custom domain.
Turn on Allow All Incoming Messages.
If the domain owner allows all incoming messages, any messages that aren’t sent to an active email address go to the domain owner’s inbox. If this setting isn’t turned on, those messages are returned to the sender.
Note: Messages sent to deleted email addresses are automatically returned to the sender.