Mailgun

Capabilities

These values come from the adapter's exported capabilities declaration. The field support matrix covers normalized message fields.

The Mailgun adapter calls the Mailgun Messages API with plain fetch. It is the one adapter that posts multipart form data instead of JSON, using Mailgun's prefixed field names: h: for headers, v: for metadata variables, o: for sending options. Every send is scoped to the domain you configure.

Mailgun@opencoredev/email-sdk/mailgun

Provider docs

Configure

Grab an API key from the Mailgun dashboard and note the sending domain it belongs to. Both are required.

import { createEmailClient } from "@opencoredev/email-sdk";
import { mailgun } from "@opencoredev/email-sdk/mailgun";

export const email = createEmailClient({
  adapters: [
    mailgun({
      apiKey: process.env.MAILGUN_API_KEY!,
      domain: process.env.MAILGUN_DOMAIN!,
    }),
  ],
});

Send

Mailgun maps every common field: cc, bcc, replyTo, headers (as h:Name), attachments (multipart attachment/inline parts by disposition), tags (values as o:tag), and metadata (as v:key variables, surfaced later in webhooks and logs). sendAt becomes a native scheduled send via o:deliverytime (RFC 2822); Mailgun accepts up to 3 days out on most plans, 7 with extended storage.

const result = await email.send({
  from: "Acme <hello@mg.acme.com>",
  to: "user@example.com",
  replyTo: "support@acme.com",
  subject: "Your receipt from Acme",
  html: "<p>Thanks for your order.</p>",
  metadata: { orderId: "ord_123" },
  tags: [{ name: "type", value: "receipt" }],
});

console.log(result.id); // Mailgun message id

The response id is Mailgun's queued message id from the response body. Match it against delivery events in webhooks or the Mailgun logs.

Personalized sends

Mailgun implements native sendPersonalized, so all recipients and variables travel in one request through Mailgun's recipient-variables field.

await email.sendPersonalized({
  message: {
    from: "Acme <hello@mg.acme.com>",
    subject: "Hi %recipient.name%",
    html: '<a href="https://acme.com/unsub?id=%recipient.id%">Unsubscribe</a>',
  },
  recipients: [
    { to: "ada@example.com", variables: { name: "Ada", id: "u_1" } },
    { to: "linus@example.com", variables: { name: "Linus", id: "u_2" } },
  ],
});

Verify from the CLI

MAILGUN_API_KEY="key-..." MAILGUN_DOMAIN="mg.acme.com" \
  npx --package @opencoredev/email-sdk email-sdk doctor --adapter mailgun

MAILGUN_API_KEY="key-..." npx --package @opencoredev/email-sdk email-sdk send \
  --adapter mailgun \
  --domain mg.acme.com \
  --from "Acme <hello@mg.acme.com>" \
  --to user@example.com \
  --subject "Mailgun smoke test" \
  --text "It works" \
  --dry-run

Credentials also work as flags: --api-key, --domain, and --base-url (or MAILGUN_BASE_URL) override the environment. Drop --dry-run for one real send to prove the domain's DNS records and the account are actually ready.

Compare Mailgun with other providers

Side-by-side message-field support from the SDK capability matrix, with working code for both adapters:

• Resend vs Mailgun
• Postmark vs Mailgun
• SendGrid vs Mailgun
• Mailgun vs AWS SES