--- title: "Test sign-up and login emails in apps built with Google Antigravity · Proxy Mail QA" description: "Antigravity usually wires login to Firebase Auth. Make sure verification and reset links reach your app, and test every login email with a private inbox." url: https://proxymail.qa/built-with/antigravity --- 1. [Home](https://proxymail.qa/) 2. [AI app builders](https://proxymail.qa/built-with) # Testing sign-up and login emails in apps you build with Antigravity Google Antigravity's agents plan, build and test your app for you. Ask for accounts and they usually reach for Firebase Authentication, Google's own login service. Its emails work out of the box, with one big catch and two settings worth checking before you launch. Updated October 15, 2026 ## Your login options with Firebase | Sign-in option | Emails your users get | Test with Proxy Mail QA | | --------------------------------------- | ------------------------------------------------------------------------------- | -------------------------- | | Email and password | A verification link (if your app sends one), password reset links, email change | Yes | | Email link (passwordless) | A link to sign in | Yes | | Google, Apple, GitHub and other buttons | None to sign in | No: use an account you own | | Phone | A text message | No | If your app uses Supabase, Clerk or another service instead, see [which emails each one sends](https://proxymail.qa/built-with/login-methods#login-services-coding-agents-use). ## Test every login email in five minutes 1. **Create an address** in Proxy Mail QA, with a generated persona if your form asks for a name. 2. **Sign up on your app.** Running it on your own machine is fine to start; check the deployed app before you launch. 3. **Open the verification link from the row.** It gets an **Open link** button, and Proxy Mail QA never opens it first. On a deployed app, if the link would bring people back to `localhost`, we flag it, even when that address is tucked inside Firebase’s own link. 4. **Check you couldn’t use the app before verifying.** 5. **Then reset the password,** sign in with the new one, and save it on the row. ## Three things to check in Firebase **1\. Unverified users.** Firebase lets people sign in as soon as they sign up, whether or not they’ve clicked the verification link. Generated code often sends the email but never checks the result. Make sure your app sends the verification email after sign-up and keeps unverified accounts on a “check your email” screen. **2\. Authorized domains.** Links that bring people back to your app after verifying, resetting a password or signing in by email only work for domains listed under **Authentication → Settings → Authorized domains**. `localhost` and your Firebase Hosting addresses are there already; add your custom domain, or links fail with `auth/unauthorized-continue-uri`. **3\. The sender.** Under **Authentication → Templates** you can change the sender’s name, send from your own domain and edit each email. Do it before launch, so people recognise who the email is from. Using email-link sign-in? Firebase changed how those links work when Dynamic Links shut down: [here’s the setup](https://proxymail.qa/mobile/firebase-email-link). ## Let the agent run the check Antigravity’s agents can use MCP servers. [Add Proxy Mail QA](https://proxymail.qa/docs/mcp#google-antigravity), then ask: Prompt ```text Create a test address with Proxy Mail QA, sign up on the running app with it, wait for the verification link and open it. Then tell me where the link went, and whether the account could use the app before it was verified. ``` ## Copy-paste prompts for Antigravity Prompt ```text List every email this app sends: verification, password reset, email-link sign-in, email change and anything else. For each, tell me what triggers it, which URL it continues to, and how long its link stays valid. Flag anything that uses localhost. ``` Prompt ```text After email and password sign-up, send a verification email and keep unverified users on a "check your email" screen with a button to send it again. Enforce it in the Firestore security rules as well, not only in the page. ``` Prompt ```text Make the verification, password reset and email-link sign-in emails continue to the deployed app's address, from an environment variable, and tell me which domain to add to Firebase's authorized domains. ``` ## Try it on your next sign-up test Free plan, no credit card. Create an address and watch the code or link arrive. [Create a free account](https://app.proxymail.qa/?mode=signup&from=antigravity) ## Questions ### Can someone sign in before they've verified their email? Yes, by default in Firebase. Verifying only marks the account as verified (emailVerified); your app has to check it and keep unverified users out of anything that needs a real address. ### Why does the verification email come from firebaseapp.com? Firebase sends from a noreply address on your project's firebaseapp.com domain until you set up your own under Authentication, Templates. Your own domain is easier for people to recognise. ### Can Antigravity's agent read the code or link itself? Yes. Add the Proxy Mail QA MCP server to Antigravity, and its agent can create an address, sign up and wait for the code or link. It gets only the code or link, never the email's text. Setup is at proxymail.qa/docs/mcp. ## Related guides - [LovableWhich Lovable Cloud logins send email, the Site URL and sender settings, and a check before you launch.](https://proxymail.qa/built-with/lovable) - [ReplitReplit Auth, Clerk Auth or your own: which send email, and how to test each on the published app.](https://proxymail.qa/built-with/replit) - [BoltTurn on email confirmation, fix the localhost Site URL and test every auth email before you publish.](https://proxymail.qa/built-with/bolt) - [Base44Test the sign-up code, password reset and invites, and every user role, with a test account per role.](https://proxymail.qa/built-with/base44) - [v0Set Supabase’s Site URL and redirects for Vercel deployments, or move Clerk to production, then test every login email.](https://proxymail.qa/built-with/v0) - [Claude CodeCheck the auth emails in apps you build with Anthropic’s coding agent, from localhost to staging.](https://proxymail.qa/built-with/claude-code) - [OpenAI CodexRun the real email flow once before you merge a Codex change that touches sign-up or login.](https://proxymail.qa/built-with/codex) - [CursorCheck the real sign-up, magic-link and reset emails after the agent changes your auth code.](https://proxymail.qa/built-with/cursor) - [QoderCheck the real sign-up, code and reset emails after the agent changes your auth code, or let it check them itself.](https://proxymail.qa/built-with/qoder) - [Login methods explainedEmail, codes, magic links, Google and Apple buttons, phone and SSO: what each sends, what breaks and how to test it.](https://proxymail.qa/built-with/login-methods) [See every email testing problem we solve](https://proxymail.qa/solve) Google, Antigravity and Firebase are trademarks of Google LLC. Proxy Mail QA is independent and isn't affiliated with or endorsed by them.