Create a new mailbox for a domain.
Email Construction: The full email address is created by combining the email username with the domain from domain ID (e.g., email=“john.doe” + domain=“example.com” = “[email protected]”).
Password: Auto-generated random password if not provided in request.
Username part of email (e.g., john.doe)
Domain ID (must be owned by user)
Relay server ID for mail routing
Password (auto-generated if not provided)
Optional project ID
Optional reply-to address
255255255255-2147483648 <= x <= 2147483647255