Datto has limited the ability to sign up for new accounts to strictly buisness related email domains. Public email domains such as @gmail.com, @outlook.com, @hotmail.com, @yahoo.com, etc will not be able to create Datto Drive subdomains.
If you do require the use of a personal email account please create your Datto Drive account with a work related email account and invite the personal email account as a user on your subdomain.
Head on over to our Community Forum or get live help.