Migrate from Postmark to RelayPost

Why teams migrate from Postmark

Postmark is a solid transactional email service with excellent deliverability. But teams outgrow it for a few common reasons:

• Postmark is transactional-only — you need a second provider for marketing and campaign emails
• Pricing starts at $15/month for 10,000 emails — RelayPost starts at $5/month for the same volume
• No free tier for testing or low-volume projects
• Message streams add complexity when you just want to send email

RelayPost handles both transactional and campaign email in one platform, with simpler pricing and a free tier for getting started.

Feature comparison

Migration steps

# Before (Postmark)
v=spf1 include:spf.mtasv.net ~all

# After (RelayPost)
v=spf1 include:relaypost.dev ~all

# During migration (both)
v=spf1 include:spf.mtasv.net include:relaypost.dev ~all

API mapping: Postmark → RelayPost

Code example: sending email

const response = await fetch(
  "https://api.postmarkapp.com/email",
  {
    method: "POST",
    headers: {
      "X-Postmark-Server-Token": "your-token",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      From: "[email protected]",
      To: "[email protected]",
      Subject: "Welcome",
      HtmlBody: "<p>Welcome aboard!</p>",
    }),
  }
);

const response = await fetch(
  "https://api.relaypost.dev/v1/emails/send",
  {
    method: "POST",
    headers: {
      "Authorization": "Bearer your-api-key",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      from: "[email protected]",
      to: "[email protected]",
      subject: "Welcome",
      html: "<p>Welcome aboard!</p>",
    }),
  }
);

Key differences: RelayPost uses lowercase field names, standard Bearer token auth, and a versioned API path.

SMTP migration

If you're using Postmark's SMTP interface, update your SMTP settings:

Webhook migration

Postmark and RelayPost both support webhooks for delivery events. Update your webhook URL in the RelayPost dashboard and adjust your handler for the new payload format:

Migration checklist

• ☐ Create RelayPost account and organization
• ☐ Add sending domain and verify DNS records
• ☐ Generate API key and/or SMTP credentials
• ☐ Update application code (API calls or SMTP config)
• ☐ Update webhook endpoints and payload handlers
• ☐ Test email sending in staging environment
• ☐ Verify delivery, bounce, and open tracking works
• ☐ Update SPF record (add RelayPost include)
• ☐ Update DKIM records for your domain
• ☐ Deploy to production
• ☐ Monitor delivery metrics for 48 hours
• ☐ Remove Postmark SPF include after confirming everything works
• ☐ Cancel Postmark subscription