To add a mail server, click on [+Server] button at the right top on the page.
You can set up Z.com.io domain, auto-backup, and size of the disk space as well at the same time.
You can create a sub-domain name as you like, and make a new email address.
A sub-domain name is not allowed to change after it is added to a mail server.
It retrieves three generations of a backup copy of the mail data regularly and automatically.
You can check the backup data in the backup server via the mail client.
You can add a disk space in 5GB increments without any limit (you can add more later).