---
title: Email guide
description: Send mail from apps through Resend over HTTP — Void's native sender is not available on Outer.
---

**Verdict: not available natively — use Resend.** Void's `sendEmail` needs
Cloudflare's `send_email` binding, which is not an accepted deploy key on
Outer (`crates/outer/src/deploy/pipeline.rs`): a config declaring it fails
deploy validation naming the key. SMTP ports 25/465/587 are blocked at the
fleet edge. Apps mail through an HTTP email API such as Resend with their
own key instead.

## 1. Store the key

Never commit it — set it outside the code and read it as a Worker env var
on the next deploy ([Secrets](/guides/celld)):

- `set_secret {app, key: "RESEND_API_KEY", value: "re_…"}` (MCP), or
  Console → Secrets.

## 2. Send over HTTP

```ts
// routes/api/invite.ts
import { defineHandler } from "void";
import { env } from "cloudflare:workers";

export const action = defineHandler(async (c) => {
  const body = await c.req.json<{ to: string }>();
  if (typeof body.to !== "string" || !body.to.includes("@")) {
    return c.json({ errors: { to: "Enter a valid email address." } }, 422);
  }
  const res = await fetch("https://api.resend.com/emails", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${env.RESEND_API_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      from: "Grocery <list@updates.example.com>",
      to: body.to,
      subject: "You're invited",
      text: "Join our grocery list: https://grocery.outer.now",
    }),
  });
  if (!res.ok) return c.json({ errors: { to: "Send failed — check the address." } }, 422);
  return {};
});
```

Use a sender domain you control (verified in Resend), and validate the
recipient before sending — bounced spam burns the domain.

## 3. Receiving

Inbound email needs a receiving service in front (Resend inbound, Cloudflare
Email Routing on your own zone) forwarding to an app route as HTTP — there
is no MX path into `<slug>.outer.now`.

## Sources

- Void email guides: <https://void.cloud/guide/email> (native pattern — not deployable on Outer)
- Secrets: [celld](/guides/celld) (Runtime rules → Secrets)