Slack + MailKite

Slack is where teams communicate. Use MailKite to forward inbound email as Slack messages — support requests, notifications, and alerts appear in the right channel instantly.

What you need

• A verified domain with SPF + DKIM published
• Your API key (mk_live_…)
• Slack workspace with an Incoming Webhook or Bot Token

How it works

MailKite POSTs inbound email to a webhook handler that sends a Slack message via the Incoming Webhook URL or Bot API. The message uses Slack Block Kit for rich formatting — subject as the header, sender/recipient as fields, and the body as the main content.

Set up the webhook

Deploy this handler as a serverless function or worker. It formats inbound email as a Slack Block Kit message and posts it to your channel. Set SLACK_WEBHOOK_URL as an environment variable.

// Slack inbound email → channel message handler

async function handleInbound(email) {
  const webhookUrl = process.env.SLACK_WEBHOOK_URL;

  const message = {
    blocks: [
      {
        type: 'header',
        text: { type: 'plain_text', text: `📧 ${email.subject || 'New inbound email'}` },
      },
      {
        type: 'section',
        fields: [
          { type: 'mrkdwn', text: `*From:*
${email.from}` },
          { type: 'mrkdwn', text: `*To:*
${email.to}` },
        ],
      },
      {
        type: 'section',
        text: { type: 'mrkdwn', text: email.text?.substring(0, 2000) || '_No body_' },
      },
    ],
  };

  const res = await fetch(webhookUrl, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(message),
  });
  return res.json();
}

Receive inbound email

Configure your MailKite domain's webhook URL to point at your handler. Every inbound email delivers this payload:

• from — sender address
• to — recipient address
• subject — email subject
• text — plain text body
• html — HTML body
• attachments — array of file objects

Test it

curl -X POST https://your-worker.example.com/mailkite-inbound \
  -H "Content-Type: application/json" \
  -d '{"from":"customer@example.com","to":"support@yourdomain.com","subject":"Need help","text":"My order #1234 is late."}'

Troubleshooting

• Create an Incoming Webhook at api.slack.com/apps → your app → Incoming Webhooks; select the target channel.
• Slack webhooks accept a max of 3000 characters — the handler truncates long email bodies automatically.
• If the webhook URL is invalid, Slack returns a 404 — check the URL in your environment variables.

See the SMTP relay docs for connection details, or Inbound webhooks for the full payload.