You need to immediately update your support system to reply if the mail address is not found in the database automatically!
We will likely never do anything like that, we have many users who don’t have accounts. In the future we may add the ability to open a support ticket directly on site.
We allow you to add secondary email addresses to your account, so if you can add the email address you’re able to send from to your account then it should resolve your issue with your email address.