When to use it
When sign-up or login emails land in spam, arrive late or don’t arrive at all, especially once real users start signing up. Apps built on Supabase often still use its built-in email service, which is meant for testing and only allows a few emails an hour.
Before you paste it, create an account with an email provider (Resend, Postmark, Amazon SES or Brevo all work) and add your domain there. Keep the SMTP details the provider gives you to hand, because your builder will ask for them.
What to check afterwards
- Add the DNS records your provider and builder list, wherever your domain is managed. Wait an hour.
- Sign up to your app with a Gmail address. The email should arrive in the inbox within a minute.
- In Gmail, open it, click the three dots, choose Show original and check that SPF, DKIM and DMARC all say
PASS.
If it doesn’t work
If the builder says it can’t change email settings, you may need to do it in the database provider’s dashboard yourself. In Supabase, it’s custom SMTP in your project’s Authentication settings. The prompt still gives you the list of DNS records you need.
The full background is in our guide: Why your sign-up emails go to spam (and how to fix it).