What is Nodemailer?

Nodemailer is a popular npm module for Node.js applications that allows you to easily send emails from your Node.js application. Some key facts about Nodemailer:

Nodemailer is an open-source Node.js module available through the npm registry.
It allows you to send emails from Node.js applications by connecting to SMTP servers for delivery.
Nodemailer works by using "transports" that know how to connect and authenticate with different email services like Gmail, Yahoo, SendGrid, MailGun, etc.
It supports features like HTML/text email, attachments, templates, bulk sending, and more.
Nodemailer handles all the complexities of sending emails for you, like MIME formatting, SMTP connections/auth, etc.

In simple terms, Nodemailer makes sending emails easy and intuitive from within Node.js applications. It's popular for adding email capabilities to Node.js backends and web applications.

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Why Use Nodemailer for Sending Email from Node.js?

Here are some of the key advantages of using Nodemailer for sending email from Node.js:

Simple and intuitive API - the Nodemailer API provides simple methods like "sendMail" to send HTML or plain text emails.
Built for Node.js - Nodemailer is made for Node environments, so you don't have to worry about using external dependencies.
Supports many email transports - connect to SMTP servers, web APIs, or even send mail locally for testing.
Handles connection pooling and retries - Nodemailer manages SMTP connections efficiently behind the scenes.
Supports modern ES6 promises - Nodemailer uses promises rather than callbacks for cleaner async code.
Robust feature set - supports attachments, templates, bulk sending, custom headers, and more.
Well maintained - has an active open-source community with frequent updates.
Large ecosystem of plugins - tap into addon capabilities like SES sending, MailGun, etc.
Easy to test locally - the ability to send test emails locally is built right in.

Nodemailer makes sending email fast, efficient, and reliable by handling all the complexity for you. The simple API paired with robust features makes it a great choice for Node.js applications.

How to Install Nodemailer?

Nodemailer is available as an npm package, so you can easily install it in your Node.js application using npm:

npm install nodemailer

Or with Yarn:

yarn add nodemailer

This will install the latest version of Nodemailer and automatically save it in your package.json file as a dependency.

Once installed, you can require/import nodemailer in your Node.js code:

const nodemailer = require('nodemailer');
import nodemailer from 'nodemailer';

And that's it - you're ready to start using Nodemailer's API to send mail!

How to Send Email with Nodemailer?

Here is a simple example of sending email with Nodemailer:

const nodemailer = require('nodemailer');


// Create transporter using SMTP transport

let transporter = nodemailer.createTransport({

  service: 'gmail',

  auth: {

    user: 'your_email@gmail.com', 

    pass: 'your_password'

  }

});


// Message options 

let mailOptions = {

  from: 'sender@email.com',

  to: 'recipient@email.com',

  subject: 'Nodemailer test',

  text: 'Hello world!'

};


// Send Email

transporter.sendMail(mailOptions, (error, info) =&gt; {

  if (error) {

    console.log(error);

  } else {

    console.log('Email sent: ' + info.response);

  }

});

Let's break this example down:

Import nodemailer module
Create a "transporter" using createTransport method
The transporter contains connection info for the SMTP server
Set message options like from, to, subject, text, etc.
Send email using transporter.sendMail() and callback
Log any errors or success response

This allows you to get started sending basic emails with Nodemailer. You can further customize with HTML, attachments, templates, and more.

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How to Send Emails to Multiple Recipients with Nodemailer?

To send emails to multiple recipients with Nodemailer, you can use the "to", "cc", and "bcc" message options:

let mailOptions = {
  // ... other options
  to: 'recipient1@email.com, recipient2@email.com', // List of recipients
  cc: 'recipient3@email.com', // List of recipients to CC
  bcc: 'recipient4@email.com, recipient5@email.com' // List of recipients to BCC
};
// Send email
transporter.sendMail(mailOptions, (err, info) =&gt; {
  // ...
});

The "to" field accepts a comma-separated list of recipients appearing in the email's "To" section.

The cc field accepts a list of recipients to carbon copy who will appear in the CC section.

The bcc field will blind carbon copy recipients without indicating them to other recipients.

This provides an easy way to send emails to multiple recipients with Nodemailer.

How to Send Emails with Gmail using Nodemailer?

To send emails using a Gmail account with Nodemailer, set the service to "gmail" and provide your Gmail credentials:

// Gmail transporter

let transporter = nodemailer.createTransport({
  service: 'gmail',
  auth: {
    user: 'your_email@gmail.com',
    pass: 'your_gmail_password' 
  }
});
// Message options ... 
// Send email
transporter.sendMail(mailOptions, (err, info) =&gt; {
  // ...
});

Gmail's SMTP server will deliver messages from your Gmail account. Ensure you first enable "Less Secure App" access in your Gmail settings.

Instead of directly using your Gmail password, you can also use OAuth2 authentication for added security.

Overall, Nodemailer makes it easy to leverage Gmail's reliable SMTP servers to send email from Node.js.

How to Send Emails with Attachments Using Nodemailer?

To send emails with attachments using Nodemailer:

Set the attachments option to an array of attachment objects containing path and filename: ```javascript let mailOptions = { // Other options attachments: [ { path: '/path/to/file.txt', filename: 'attachment.txt' } ] }; ```
Make sure you add the proper MIME type, like multipart/mixed, when sending:

let mailOptions = {
  // Other options
  // Set multipart to mixed 
  multipart: 'mixed' 
};
// Send mail with defined transport object

transporter.sendMail(mailOptions, (error, info) =&gt; {
  //...
});

The multipart: 'mixed' tells the receiving client that a mixed mode email is sent with text and one or more attachments.

And that's all you need to start sending emails with attachments using Nodemailer!

How to Send HTML Emails with Nodemailer?

To send HTML emails with Nodemailer:

Set HTML field instead of text in mail options: ```javascript let mailOptions = { // Other options // HTML body html: '<h1>Hello World!</h1><p>This is an HTML email</p>' }; ```

Specify MIME type as multipart/alternative:

let mailOptions = {
  // Other options

  // MIME
  multipart: 'alternative' 
};

Send mail as usual: ```javascript transporter.sendMail(mailOptions, (error, info) => { //... }); ```

The multipart/alternative tells email clients that an HTML alternative is provided. Most clients will default to displaying HTML if available.

You can also provide both text and html options to send multi-part emails with both text and HTML versions.

How to Create Email Templates with Nodemailer?

To use templates with Nodemailer:

Install a templating engine like Handlebars:

npm install handlebars

Create a template file like email-template.handlebars

Compile the template:

const handlebars = require('handlebars');
const template = handlebars.compile(source);

Render the template into an HTML email body: ```javascript let mailOptions = { // Other options html: template({ name: 'John' }) } ```
Set subject and other options
Send as usual with the transporter

This allows you to create reusable email templates for common emails like welcome messages, receipts, notifications etc.

Other templating engines like Pug, EJS also work well with Nodemailer. The key is compiling templates into HTML and using them as an email body.

How to Send Bulk Emails with Nodemailer?

To send bulk emails with Nodemailer:

Create a transporter with pool: true to enable pooling: ```javascript let transporter = nodemailer.createTransport({ pool: true, // ...other options }); ```
Use a loop to generate and send emails: ```javascript // Recipients list const recipients = ['email1@test.com', /*...*/]; recipients.forEach(recipient => { // Mail options let mailOptions = { to: recipient, // Other options... }; // Send email transporter.sendMail(mailOptions, (err, info) => {}); }); ```
The transporter will manage connections from the pool to send to all recipients efficiently.
For very large lists, batch recipients into smaller sets.

Nodemailer is designed to efficiently send bulk emails by managing SMTP connection pooling, retries, and batch sending behind the scenes.

Conclusion

Nodemailer provides a simple and efficient way to add email capabilities to your Node.js applications. With its intuitive API, support for many transports, and robust feature set, Nodemailer handles all the complexities of sending emails for you.

I hope these frequently asked questions provide a useful overview of how to use Nodemailer to send emails from Node.js. Let me know if you have any other Nodemailer questions!

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