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Testing sign-up emails in apps built on Replit

Replit Agent can build, run and publish a full app with accounts. If your app sends its own emails (sign-up confirmations, codes, password resets, invites), make sure they arrive and point at the app your users will actually visit.

Updated

Two addresses for one app

While you build, Replit runs your app on a development URL connected to your workspace. When you publish, it gets a public address (or your custom domain). Sign-up and reset emails should always link to the published one.

Auth code that was written and tested in the workspace often picks up the development URL, or localhost, as its base address. It works for you and fails for everyone else.

Check your app’s emails

  1. Create an address in Proxy Mail QA. Add a generated persona if your sign-up form asks for a name or username.
  2. Sign up on the published app, not in the workspace preview.
  3. Open the code or link from the row. Codes have a Copy button; links become Activate account, Sign in or Reset password.
  4. Check where the link goes. If it points at localhost or a private address, we flag it. If it points at the development URL, that’s your clue the base URL isn’t set for the published app.
  5. Test password reset and any invites the same way, then save the account’s password on the row.

Ask the Agent for something specific: “Emails from the published app link to the development URL. Use the published domain as the base URL for all email links, from an environment variable.” If your app uses Supabase Auth, also check its Site URL and Redirect URLs: here’s how.

If emails don’t arrive

Try it on your next sign-up test

Free plan, no credit card. Create an address and watch the code or link arrive.

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Questions

My verification link opens the development URL. Is that a problem?

Yes, for real users. The development URL is tied to your workspace while you build. Emails sent by the published app should link to its published address or your custom domain.

Does this work with Supabase, Firebase or Clerk on Replit?

Yes. Proxy Mail QA receives whatever email your app or its auth provider sends to the address you signed up with.

Can I test several user roles?

Yes. Create a batch of addresses, each with a generated name and username, and use one per role, such as admin, member and guest. Notes and tags keep track of which is which.

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Replit is a trademark of Replit, Inc. Proxy Mail QA is independent and isn't affiliated with or endorsed by them.