Migrate from Mailgun

What changes, what doesn't

Both are per-domain, developer-first sending APIs with webhooks for delivery events, so the integration shape survives. The concrete change with the widest blast radius: Mailgun's HTTP API is form-encoded (multipart/form-data or application/x-www-form-urlencoded), while EuroMail's is JSON. If your client builds a FormData object today, that code needs to change, not just the field names. The honest comparison, including where Mailgun is the better choice, is at euromail vs Mailgun.

Verify your domain on EuroMail first, run both in parallel, then cut over.

API mapping

The endpoint itself simplifies: no per-domain path segment, because your API key is already scoped to your account and the from address determines the sending domain (which must be verified first).

Code before and after

curl:

# Before: Mailgun (form-encoded, HTTP Basic auth)
curl -X POST https://api.mailgun.net/v3/yourdomain.com/messages \
  -u "api:your-mailgun-api-key" \
  -F from="[email protected]" \
  -F to="[email protected]" \
  -F subject="Welcome aboard" \
  -F html="<h1>Welcome!</h1>"

# After: EuroMail (JSON, header auth)
curl -X POST https://api.euromail.dev/v1/emails \
  -H "X-EuroMail-Api-Key: em_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "[email protected]",
    "to": "[email protected]",
    "subject": "Welcome aboard",
    "html_body": "<h1>Welcome!</h1>"
  }'

TypeScript:

// Before: Mailgun
import formData from "form-data";
import Mailgun from "mailgun.js";
const mailgun = new Mailgun(formData);
const mg = mailgun.client({ username: "api", key: process.env.MAILGUN_API_KEY! });

await mg.messages.create("yourdomain.com", {
  from: "[email protected]",
  to: "[email protected]",
  subject: "Welcome aboard",
  html: "<h1>Welcome!</h1>",
});

// After: EuroMail
import { EuroMail } from "@euromail/sdk";
const client = new EuroMail({ apiKey: process.env.EUROMAIL_API_KEY! });

await client.emails.send({
  from: "[email protected]",
  to: "[email protected]",
  subject: "Welcome aboard",
  html_body: "<h1>Welcome!</h1>",
});

The SDK swap removes the form-encoding concern entirely. Python, Rust, and Go SDKs all send JSON with the same field names.

SMTP cutover

The username convention changes the most: Mailgun issues a separate SMTP password per sending domain, while EuroMail's SMTP relay authenticates with your account-level API key under the literal username apikey. The same convention SendGrid, Postmark, and SES SMTP presets use, so most "SMTP provider" dropdowns work unchanged. Full walkthroughs in Send Email via SMTP.

DNS: verify your domain before switching

1. Add your domain in the EuroMail dashboard and publish its DKIM, SPF, and DMARC records. Domain Verification.
2. Keep Mailgun's records in place during the dual-run. Different DKIM selectors and stacked SPF include:s let both providers verify at once.
3. Remove Mailgun's records after cutover, on your own schedule.

Webhook event mapping

Signature verification changes: Mailgun signs with HMAC-SHA256 over a concatenated timestamp + token, delivered as three separate payload fields you combine yourself. EuroMail signs the whole payload once with HMAC-SHA256 in the X-EuroMail-Signature header. One hash instead of reconstructing the signed string. See Webhooks.

Bring your suppression list

Export bounces, complaints, and unsubscribes from the Mailgun dashboard, then replay them:

curl -X POST https://api.euromail.dev/v1/suppressions \
  -H "X-EuroMail-Api-Key: em_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "email_address": "[email protected]",
    "reason": "migrated from Mailgun: hard bounce"
  }'

Details in Suppression Lists.

Your first 24 hours

Every new account spends its first 24 hours -- counted from account creation, not from your first send -- inside a probation window with two limits designed to stop day-one spam blasts without starving a real migration:

• A send-rate cap: 5 emails per minute and 25 per hour on day one, loosening over the first week.
• A recipient allowance: a token bucket of 20 that refills at 2 per hour, counted per deliverable recipient (to plus every cc and bcc). A settled, non-zero invoice raises the allowance to 1,000 -- a paid plan still inside its trial does not count as a payment. The allowance lifts entirely once the account is 24 hours old.

A refused send returns 429 with a retry-after header (the SMTP relay returns 452, which well-behaved mailers retry). Test sends from a not-yet-verified domain to your own address (sandbox mode) never consume the allowance, so integration testing is free.

The practical consequence for a migration: create your EuroMail account and verify your domain at least a day before cutover. By the time production traffic moves, the recipient allowance has expired and only the loosened week-one rate cap (15/minute, 75/hour) remains. If you must cut over with real volume on day one, settle your first invoice first -- 1,000 recipients covers a typical day -- or keep Mailgun running in parallel for the first 24 hours.

Honest gaps

• Mailing lists don't port as-is. Mailgun's mailing-list feature ([email protected] expansion) has no direct equivalent. Recipient fan-out belongs in your application, or in Contact Lists + Newsletters for marketing sends.
• Route-based inbound rules are structured differently. Mailgun's regex-match routing maps to EuroMail's inbound routes, but the rule syntax isn't a drop-in port. Expect to recreate routing logic, not copy-paste it.
• Full comparison at euromail vs Mailgun.

Cutover checklist

1. Create a EuroMail account at least 24 hours before cutover (probation limits expire with account age) and an API key with the emails:send scope (API Keys).
2. Verify your sending domain; confirm DKIM/SPF/DMARC show green.
3. Register your webhook endpoint and swap the signature verification.
4. Import suppressions from your Mailgun export.
5. Switch from form-encoded requests to JSON. Update the endpoint, auth method (Basic → header), and field names (or the SMTP username/password), accepting 202 as success instead of 200.
6. Send a staging email end-to-end; confirm the delivered webhook arrives.
7. Cut production traffic over; watch the first hour in Analytics and Deliverability Insights.
8. Keep Mailgun read-only for a rollback window, then retire it.