Add email verification to v0 apps in one prompt.
Paste a single prompt into v0 and it generates a signup form plus the server action that wires vrfymail's API. Export to your Next.js project intact — there's no SDK to install, just a fetch call.
Note: if you landed here trying to fix the v0.app student-email-verification error on your own account, that's a different page — see the Vercel community forum. This page is for developers using v0 to build apps that need email verification in their signup forms.
The v0 prompt
Open v0, start a new chat, paste this. v0 returns a signup form using shadcn/ui components and a server action that calls vrfymail. You can iterate on the UI without losing the verification logic — the server action is independent.
Build a signup form with email verification.
The form has fields: email, password, name. On submit, the form calls a Next.js
server action that verifies the email before creating the account.
Server action: POST to https://vrfymail.com/v1/check with header
Authorization: Bearer ${process.env.MAIL_VERIFIER_KEY}
and JSON body
{ "email": "<email>", "strict": true }
Response shape:
- result: "deliverable" | "undeliverable" | "risky" | "unknown"
- reason: machine code (string)
- reason_message: end-user copy already mapped (string)
- did_you_mean: typo correction or null
Handling:
- did_you_mean non-null → show inline "Did you mean <suggestion>?" with a
one-click button to apply it.
- undeliverable → block submit, show reason_message under the field.
- risky with reason "role_account" → soft yellow warning, allow submit.
- deliverable or unknown → continue with signup.
Use shadcn/ui Form, Input, Button components. Show validation state inline.
Don't install any SDK — use plain fetch.In your v0 project, open the Environment tab and add MAIL_VERIFIER_KEY=vk_live_... Redeploy the preview to pick it up.
Click Add to codebase to push to GitHub, or download the code and paste into your local Next.js app. No SDK to install — fetch travels intact.
The server action v0 generates
The form (shadcn/ui Input + Button + Form, with inline validation states) gets generated alongside this server action. The form imports verifyEmail and calls it on submit.
// app/actions/verify-email.ts
"use server";
export async function verifyEmail(email: string) {
const r = await fetch("https://vrfymail.com/v1/check", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.MAIL_VERIFIER_KEY}`,
"Content-Type": "application/json",
},
body: JSON.stringify({ email, strict: true }),
// No cache — verdicts are per-customer and 24h-cached server-side already.
cache: "no-store",
});
const verdict = await r.json() as {
result: "deliverable" | "undeliverable" | "risky" | "unknown";
reason: string;
reason_message: string;
did_you_mean: string | null;
};
if (verdict.did_you_mean) {
return { ok: false, suggestion: verdict.did_you_mean, error: `Did you mean ${verdict.did_you_mean}?` };
}
if (verdict.result === "undeliverable") {
return { ok: false, error: verdict.reason_message, code: verdict.reason };
}
if (verdict.result === "risky" && verdict.reason === "role_account") {
return { ok: true, warn: verdict.reason_message };
}
// deliverable + unknown both pass.
return { ok: true };
}
On unknown, accept the signup.
unknown is what you get when the verification pipeline couldn't reach a verdict in the time budget. DNS lookup failed. MX timed out. None of those are evidence the email is bad — they're evidence the network had a bad second.
v0's default generations sometimes fail-closed (block on anything that isn't deliverable). The prompt above patches that — deliverable and unknown both pass.
On vrfymail the cost-side argument vanishes too: unknown verdicts don't bill. refundUsage() releases the slot when the pipeline can't reach a verdict.
- deliverable Accept.
- unknown Accept. Log the verdict if you want a paper trail. Not billed.
- risky
role_account→ soft warning, allow submit. Other reasons → block or quarantine. - undeliverable Block. Show
reason_messageverbatim. - did_you_mean Non-null → suggest the correction inline. Works on any verdict.
v0 ships forms. vrfymail ships verdicts. Both fit in one fetch.
v0's strength is generating production-shaped React + Next.js code from a description. Its weakness is that "production-shaped" often skips edge cases — fail-closed validation, role-account handling, typo suggestions are easy to miss in a prompt.
vrfymail's response is shaped to be slotted directly into UI: reason_message is end-user copy you can show verbatim, did_you_mean is a one-click correction, role_account as a soft-warning category instead of a hard block. The prompt above gives v0 the shape — the verdict gives v0 the content.
Same pattern works across the other AI coding tools — Cursor via .cursor/rules/email-verify.mdc, Claude Code via CLAUDE.md, and seven more on the AI builders hub.
v0 + email verification, answered
- How do I add the MAIL_VERIFIER_KEY env var in v0?
- Open the v0 chat for your project, click the Environment tab in the project settings, add MAIL_VERIFIER_KEY=vk_live_... Then redeploy the preview. The env var is injected at runtime — the generated code references process.env.MAIL_VERIFIER_KEY directly.
- Can I export the v0 code into my own Next.js project?
- Yes. v0 generates standard Next.js 15 app-router code. Click 'Add to codebase' to push the server action and form into a connected GitHub repo, or download the code and paste it into your project. The vrfymail integration travels intact because there's no SDK — just the fetch call.
- Does v0 support running the server action in its preview?
- Yes, v0 runs server actions in the hosted preview environment. As long as MAIL_VERIFIER_KEY is set in v0's Environment tab, you can test the full signup flow inside v0 before exporting. The preview hits production vrfymail — call it part of the 5,000/month free tier.
- What if I want client-side validation feedback as the user types?
- Ask v0 to add a debounced verifyEmail call on the email field's onBlur or after a 500ms typing pause. The server action remains the same; the client just calls it earlier. Most v0 generations will scaffold the debounce + state machine correctly if you specify it in the prompt.
- Does this work with v0's Vercel AI SDK integrations too?
- Yes. The vrfymail call is independent of any AI SDK v0 wires in. If your generated app uses streamUI or @ai-sdk/* hooks, the verifyEmail server action sits alongside them — it's just a fetch. No conflicts, no shared dependencies.
One prompt. One server action. Real verdicts.
vrfymail's /v1/check returns a verdict in 50ms p50. Free tier: 5,000 verifies/month, no card. Paid plans start at $9/mo for 10,000 — see pricing.