Cloudflare Email Service

This service provides a worker that sends emails via Cloudflare's integration with MailChannels. This allows your other workers (local and deployed) or external services to send emails via HTTP.

Requirements

• Cloudflare account
• Wrangler CLI authenticated

Getting Started

1. Run npm install
2. (Optional) Add a custom domain route in wrangler.toml to the a domain you wish to use for the email service.
   • This domain is for the worker service and can be different than your outgoing email address domain.
3. Update the DKIM_DOMAIN and DKIM_SELECTOR vars in wrangler.toml
   • DKIM_DOMAIN is the outgoing email domain
   • DKIM_SELECTOR will be the prefix to your _domainkey TXT record
   • The TXT DKIM DNS record will be at [DKIM_SELECTOR]._domainkey.[DKIM_DOMAIN].
4. Run npm run deploy to deploy the worker
5. Run npm run reset-dkim and create or update your DKIM TXT DNS record
6. Run npm run reset-key and save the X-API-Key
7. Create or update an existing SPF TXT record to contain include:relay.mailchannels.net.
   • For example [DKIM_DOMAIN]. 1 IN TXT "v=spf1 include:relay.mailchannels.net include:_spf.mx.cloudflare.net ~all".
   • Having multiple TXT SPF records is invalid. You must combine an existing SPF record using multiple include:.
8. Create a _mailchannels TXT DomainLockdown Record
   • NOTE: the cfid is the domain that your worker is running under. It can be different than the DKIM and SPF domain, which is the domain of outgoing emails.
   • For example _mailchannels.[DKIM_DOMAIN]. 1 IN TXT "v=mc1 cfid=[YOUR_WORKERS_DEV_DOMAIN].workers.dev"
   • The cfid does not include the subdomain of the worker.

Using the Service

When submitting requests, you can add the query parameter /?dry-run=true. This will test the API and can be used for testing without sending emails.

workers.dev domains can be used to host your worker. However, you can not use that domain for your outgoing email address since DKIM and SPF will not be available.

You can call the email service with a POST using the same body content as the MailChannels Transactional API and a X-API-Key header set to the generated API key from Getting Started. DKIM parameters will automatically be added.

Example Request

POST /?dry-run=false
Host: mailchannels.example.com
Content-Type: application/json
X-API-Key: YOURGENERATEDKEY

{
  "from": {
    "email": "[email protected]",
    "name": "Test Sender"
  },
  "replyTo": {
    "email": "[email protected]",
    "name": "Example Support"
  },
  "personalizations": [
    {
      "to": [
        {
          "email": "[email protected]",
          "name": "Test Recipient"
        }
      ],
      "bcc": [
        {
          "email": "[email protected]",
          "name": "Test BCC Recipient"
        }
      ],
      "cc": [
        {
          "email": "[email protected]",
          "name": "Test CC Recipient"
        }
      ]
    }
  ],
  "subject": "Example Email",
  "content": [
    {
      "type": "text/plain",
      "value": "Text message content"
    }
  ]
}