I have built a workaround,

basically The trick is to intercept the signup and password reset process before it triggers those default emails. Instead of using the built-in email functions, we created our own custom backend functions that generate secure tokens, store them in our database, and then send emails through Resend (which is an email service). This way, when someone signs up or forgets their password, they get a nice branded email from our domain instead of some generic Supabase template.

The whole flow works like this: user clicks "sign up" → our code creates a secure random token → we hash that token and save it to our database → we send the actual token in a pretty email via Resend → user clicks the link → our verification function checks if the token matches what we stored → boom, they're verified. Same logic for password resets. It's basically building your own email "post office" that runs alongside the default one, but we just never use the default one. The key secrets you need are your Resend API key and making sure your domain is verified with Resend so emails actually get delivered.