Plugins

Nodemailer is designed to be extensible. You can inject custom logic at three well‑defined phases of a message’s lifecycle:

Phase	Keyword	When it runs	Typical uses
Pre‑processing	compile	Right after the message object is built, before the MIME source is generated	Templating, automatic plain‑text alternatives, address validation
Processing	stream	While the MIME stream is being generated	DKIM signing, inlining images, transforming HTML
Sending	transport	After the message source is ready, to actually deliver it	SMTP, SES, SparkPost, custom HTTP APIs

tip

Prefer compile and stream plugins for portability. Transport plugins are only required when you need complete control over delivery.

Writing a plugin

// commonjs — works on Node.js ≥ 6.0.0
module.exports = function myCompilePlugin(mail, callback) {
  // `mail` is the Nodemailer Mail object
  // Add or adjust properties before the MIME source is generated
  if (!mail.data.text && mail.data.html) {
    mail.data.text = require("html-to-text").htmlToText(mail.data.html);
  }

  callback(); // Always invoke the callback (or pass an Error)
};

Register the plugin on a transport instance:

const nodemailer = require("nodemailer");
const transport = nodemailer.createTransport({ sendmail: true });

transport.use("compile", require("./myCompilePlugin"));

Error handling

If your plugin encounters a fatal problem, pass an Error object to the callback:

callback(new Error("Template not found"));

The message will not be sent and the error will propagate to the caller’s sendMail() callback/promise.

Public plugins

A curated selection of community‑maintained plugins:

• express‑handlebars – Render Handlebars templates from your Express views directory. https://github.com/yads/nodemailer-express-handlebars
• inline‑base64 – Convert inline base64‑encoded images to CID attachments. https://github.com/mixmaxhq/nodemailer-plugin-inline-base64
• html‑to‑text – Automatically generate a plain‑text version when one is missing. https://github.com/andris9/nodemailer-html-to-text

Looking for something else? Try searching npm for “nodemailer plugin”.

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Need more power? See Creating plugins » for a deep dive into the plugin API.