**TL;DR:** Send mail from a Next.js route handler without leaking the key to the client: initialize @sendgrid/mail in the route, validate input, and return SendGrid's real error body. Never import this module or the key into a client component. Validate the address yourself; a bad address gives a 400 you could have avoided.

## The error

```text
)) {
    return Response.json({ error:
```

## The fix

app/api/invite/route.js:

import sgMail from '@sendgrid/mail'
sgMail.setApiKey(process.env.SENDGRID_API_KEY)

export async function POST(req) {
  const { email } = await req.json()
  if (!email || !email.includes('@')) {
    return Response.json({ error: 'valid email required' }, { status: 400 })
  }
  try {
    await sgMail.send({
      to: email,
      from: '[YOUR_VERIFIED_SENDER]', // verified sender
      subject: 'Your invite',
      text: 'Welcome aboard',
    })
    return Response.json({ sent: true }, { status: 202 })
  } catch (error) {
    const body = error.response && error.response.body
    console.error(body)
    return Response.json({ sent: false, detail: body }, { status: 502 })
  }
}

Rules:
1. The key lives in server env only. Never import this module or the key into a client component.
2. Validate the address yourself; a bad address gives a 400 you could have avoided.
3. Rate-limit the route or add a captcha if it is public; an open mail endpoint gets abused fast.

## When to use this

- You are seeing this exact error message; match the block above, not just part of it.
- The failing call matches the scenario in the title: SendGrid in a Next.js API route.
- You want the fastest verified fix before digging through logs.

## When not to use this

- Your error text differs from the block above; close cousins often have different causes.
- The stack trace points at a different component than the one in the title.
- You already applied this fix and the error persists; look for a second cause instead of reapplying.

## Compatibility

- Not pinned to a specific version; follows current SendGrid behavior.

---

## Vectle citations

- Exact version: <https://vectle.com/skills/skl_nd2FzfU077ibaDb5SPSQng/versions/skv_xEd12lc3rQKJ1F_UHoutaA>
- Canonical HTML skill page: <https://vectle.com/skills/skl_nd2FzfU077ibaDb5SPSQng>
- Current Markdown URL: <https://vectle.com/skills/skl_nd2FzfU077ibaDb5SPSQng/markdown>

## Selected public attribution and original notices/references

```json
{
  "author": "issueatlas",
  "client": null,
  "notices_and_references": [
    "https://github.com/sendgrid/docs/blob/develop/content/docs/for-developers/sending-email/quickstart-nodejs.md",
    "https://docs.sendgrid.com/api-reference/mail-send/mail-send"
  ]
}
```