Cloudflare Workers Quickstart

Prerequisites

To get the most out of this guide, you’ll need to:

Create a SendPost Account
Cloudflare Account (free tier works)
Wrangler CLI installed
A Sub-Account API Key from your SendPost dashboard

You can find your API keys in your SendPost Dashboard. Make sure to use your Sub-Account API Key for sending emails.

1. Install Wrangler CLI

npm install -g wrangler

2. Initialize Worker

wrangler init sendpost-email
cd sendpost-email

3. Basic Email Worker

Update src/index.ts:

TypeScript

export interface Env {
  SENDPOST_API_KEY: string;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Handle CORS
    if (request.method === 'OPTIONS') {
      return new Response(null, {
        headers: {
          'Access-Control-Allow-Origin': '*',
          'Access-Control-Allow-Methods': 'POST, OPTIONS',
          'Access-Control-Allow-Headers': 'Content-Type',
        },
      });
    }

    if (request.method !== 'POST') {
      return new Response(
        JSON.stringify({ error: 'Method not allowed' }),
        {
          status: 405,
          headers: {
            'Content-Type': 'application/json',
            'Access-Control-Allow-Origin': '*',
          },
        }
      );
    }

    try {
      const { to, subject, htmlBody, textBody } = await request.json();

      if (!to || !subject || !htmlBody) {
        return new Response(
          JSON.stringify({
            success: false,
            error: 'Missing required fields: to, subject, htmlBody',
          }),
          {
            status: 400,
            headers: {
              'Content-Type': 'application/json',
              'Access-Control-Allow-Origin': '*',
            },
          }
        );
      }

      // Prepare email message
      const emailMessage = {
        from: {
          email: 'hello@playwithsendpost.io',
          name: 'SendPost',
        },
        to: [{ email: to }],
        subject,
        htmlBody,
        textBody: textBody || htmlBody.replace(/<[^>]*>/g, ''),
        trackOpens: true,
        trackClicks: true,
      };

      // Send email via SendPost API
      const response = await fetch('https://api.sendpost.io/api/v1/subaccount/email/', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'X-SubAccount-ApiKey': env.SENDPOST_API_KEY,
        },
        body: JSON.stringify(emailMessage),
      });

      if (!response.ok) {
        const error = await response.text();
        throw new Error(`SendPost API error: ${error}`);
      }

      const result = await response.json();

      return new Response(
        JSON.stringify({
          success: true,
          messageId: result.messageId,
        }),
        {
          status: 200,
          headers: {
            'Content-Type': 'application/json',
            'Access-Control-Allow-Origin': '*',
          },
        }
      );
    } catch (error: any) {
      console.error('SendPost error:', error);
      return new Response(
        JSON.stringify({
          success: false,
          error: error.message,
        }),
        {
          status: 500,
          headers: {
            'Content-Type': 'application/json',
            'Access-Control-Allow-Origin': '*',
          },
        }
      );
    }
  },
};

4. Configure Worker

Update wrangler.toml:

name = "sendpost-email"
main = "src/index.ts"
compatibility_date = "2023-10-30"

[vars]
# Environment variables (use secrets for sensitive data)

5. Set Secrets

Set the API key as a secret:

wrangler secret put SENDPOST_API_KEY

Enter your Sub-Account API Key when prompted.

6. Deploy Worker

Deploy to Cloudflare:

wrangler deploy

7. Common Use Cases

Welcome Email Worker

Create src/welcome-email.ts:

TypeScript

export interface Env {
  SENDPOST_API_KEY: string;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    if (request.method === 'OPTIONS') {
      return new Response(null, {
        headers: {
          'Access-Control-Allow-Origin': '*',
          'Access-Control-Allow-Methods': 'POST, OPTIONS',
          'Access-Control-Allow-Headers': 'Content-Type',
        },
      });
    }

    try {
      const { email, firstName } = await request.json();

      if (!email || !firstName) {
        return new Response(
          JSON.stringify({
            success: false,
            error: 'Missing required fields: email, firstName',
          }),
          {
            status: 400,
            headers: {
              'Content-Type': 'application/json',
              'Access-Control-Allow-Origin': '*',
            },
          }
        );
      }

      const emailMessage = {
        from: {
          email: 'hello@playwithsendpost.io',
          name: 'SendPost',
        },
        to: [
          {
            email,
            name: firstName,
            customFields: { firstName },
          },
        ],
        subject: 'Welcome {{firstName}}!',
        htmlBody: `
          <h1>Welcome, {{firstName}}!</h1>
          <p>Thank you for joining us. We're excited to have you on board.</p>
          <p>Get started by exploring our features:</p>
          <ul>
            <li>Feature 1</li>
            <li>Feature 2</li>
            <li>Feature 3</li>
          </ul>
          <p>If you have any questions, just reply to this email.</p>
          <p><a href="{{unsubscribe}}">Unsubscribe</a></p>
        `,
        textBody: `
          Welcome, {{firstName}}!
          
          Thank you for joining us. We're excited to have you on board.
          
          Get started by exploring our features:
          - Feature 1
          - Feature 2
          - Feature 3
          
          If you have any questions, just reply to this email.
          
          Unsubscribe: {{unsubscribe}}
        `,
        groups: ['welcome'],
        trackOpens: true,
        trackClicks: true,
      };

      const response = await fetch('https://api.sendpost.io/api/v1/subaccount/email/', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'X-SubAccount-ApiKey': env.SENDPOST_API_KEY,
        },
        body: JSON.stringify(emailMessage),
      });

      const result = await response.json();

      return new Response(
        JSON.stringify({
          success: true,
          messageId: result.messageId,
        }),
        {
          status: 200,
          headers: {
            'Content-Type': 'application/json',
            'Access-Control-Allow-Origin': '*',
          },
        }
      );
    } catch (error: any) {
      return new Response(
        JSON.stringify({
          success: false,
          error: error.message,
        }),
        {
          status: 500,
          headers: {
            'Content-Type': 'application/json',
            'Access-Control-Allow-Origin': '*',
          },
        }
      );
    }
  },
};

8. Testing Locally

Run locally:

wrangler dev

Test your worker:

curl -X POST http://localhost:8787 \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@example.com",
    "subject": "Test Email",
    "htmlBody": "<h1>Hello from Cloudflare Workers!</h1>"
  }'

9. Using with Pages Functions

If using Cloudflare Pages, create functions/send-email.ts:

TypeScript

export async function onRequestPost(context: EventContext) {
  const { request, env } = context;
  // Same implementation as above
}

Make sure your sender email domain is verified in your SendPost account before sending emails.

10. Next Steps

Explore more examples and use cases: