MailerSend

MailerSend

@opencoredev/email-sdk/mailersend

OfficialNot API testedRequest tested

MailerSend supports transactional sends with CC, BCC, one reply-to address, custom headers, tag values, and attachments.

Before live sends

Create a MailerSend API token, verify the sending domain, and confirm the account plan supports any custom headers you send. MailerSend documents custom headers as Professional and Enterprise features, so lower-plan accounts should omit headers.

Configure

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

const email = createEmailClient({
  adapters: [mailersend({ apiKey: process.env.MAILERSEND_API_KEY! })],
});

Send

const result = await email.send({
  from: "Acme <hello@acme.com>",
  to: [{ email: "user@example.com", name: "Ada" }],
  cc: "billing@example.com",
  replyTo: "support@example.com",
  subject: "Invoice ready",
  html: "<p>Your invoice is ready.</p>",
  headers: {
    "X-Invoice-ID": "inv_123",
  },
  tags: [{ name: "type", value: "invoice" }],
});

console.log(result.provider, result.id);

MailerSend supports one replyTo address. The adapter rejects multiple reply-to addresses before it calls the API.

Send with an attachment

await email.send({
  from: "Acme <hello@acme.com>",
  to: "user@example.com",
  subject: "Invoice ready",
  html: "<p>Your invoice is attached.</p>",
  attachments: [
    {
      filename: "invoice.txt",
      content: "Invoice inv_123",
      contentType: "text/plain",
    },
  ],
});

Options

Option	Type	Required	Notes
`apiKey`	`string`	Yes	MailerSend API token.
`baseUrl`	`string`	No	Defaults to `https://api.mailersend.com`.
`fetch`	`typeof fetch`	No	Useful for tests or custom runtimes.

See field support for supported message fields.

MailerSend custom headers map to headers. MailerSend documents custom headers as available on Professional and Enterprise accounts, so lower-plan accounts may need to omit headers.

Response

The adapter uses the x-message-id response header when available, then falls back to body message_id or id.

CLI smoke test

MAILERSEND_API_KEY="..." npx email-sdk send \
  --adapter mailersend \
  --from "Acme <hello@acme.com>" \
  --to user@example.com \
  --subject "MailerSend test" \
  --text "It works"