Currently, SinoSend sends email notifications from the sinosend.com domain. Your explanation is that it's necessary to ensure delivery. However, you can certainly send emails on behalf of another domain without causing delivery problems. It's just a matter of adding DKIM and SPF records to authorize your server to send emails from our domain. Since we're already adding the CNAME record, this shouldn't be an inconvenience for anyone and it would look much more professional. When sending the setup instructions for a custom domain, you can simply include the additional instructions for creating the necessary email authentication records.