Node.js Mail Send Guide: Send and receive emails using NodeMailer

This article will guide you on how to send and receive emails using Node.js and solve common problems. NodeMailer is a popular npm module with more than three million downloads per week, but requires SMTP server support.

Core points:

• NodeMailer is the most commonly used npm module for Node.js applications to send emails. It has more than three million downloads per week and requires an SMTP server.
• Due to the different rendering engines and restrictions of different email clients, it is challenging to create HTML messages that are compatible with various clients. Tools and resources such as prefabricated templates, design tools, and email markup languages ??can simplify the process.
• To ensure reliability, it is recommended to send mail data to the task queue instead of sending mail directly in the Node.js application. This way, users can continue to use the application while processing messages.
• Use modules such as ImapFlow to read received emails in Node.js applications, which is very useful for handling service registration, unsubscribe requests, automation support, etc.

Send an email

Most web applications require sending emails such as registration, password reset, status reports, and complete marketing campaigns such as newsletters and promotions. This tutorial explains how to send emails in Node.js, and the concepts and challenges apply to other systems as well.

You can find many email-related modules on npm. The most popular one is NodeMailer.

Using NodeMailer requires an SMTP server to send mail. You can use your own email provider, but this demo uses the free WPOven Test SMTP Server.

1. Create a project:

mkdir emailtest
cd emailtest

2. Create package.json:

{
  "name": "emailtest",
  "type": "module",
  "main": "index.js",
  "dependencies": {
    "nodemailer": "^6.0.0"
  }
}

3. Installing NodeMailer:

npm install

4. Writing index.js:

import nodemailer from 'nodemailer';

const transporter = nodemailer.createTransport({
  host: 'smtp.freesmtpservers.com',
  port: 25
});

try {
  const send = await transporter.sendMail({
    from: '"測試郵件" <test@email.com>',
    to: 'your_email@example.com',
    subject: '你好！',
    text: '你好，世界！',
    html: '<p>你好，世界！</p>',
  });

  console.dir(send, { depth: null, color: true });
} catch (e) {
  console.dir(e, { depth: null, color: true });
}

(Please change the to: address to your own email address)

After running the code, you should see results with 250 OK response and messageId. Enter your email address on the WPOven Test SMTP Server page, click "Access Inbox" to view the "Hello!" email.

NodeMailer Basics

To send a mail, you must create a NodeMailer transporter object to define the service type. SMTP is the most common, but other services are available. Authentication user ID and password are usually required:

import nodemailer from 'nodemailer';

const transporter = nodemailer.createTransport({
  host: 'smtp.yourserver.com',
  port: 587,
  auth: {
    user: 'myid@yourserver.com',
    pass: 'my-password'
  },
});

You can use the sendMail() method of the transporter to send an email to one or more recipients:

const send = await transporter.sendMail({
  from: '"測試郵件" <test@email.com>',
  to: 'someone@example.com, sometwo@example.com',
  cc: 'somethree@example.com',
  bcc: 'somefour@example.com',
  subject: '你好！',
  text: '純文本郵件內(nèi)容',
  html: '<p>HTML郵件內(nèi)容</p>',
});

All mail clients support plain text messages. When the mail client supports HTML, you can also send rich format versions of the same message (see below for details).

NodeMailer provides many other message options, but the most common is attachments. An array of objects defines file names and contents. For example:

mkdir emailtest
cd emailtest

Send service and asynchronous architecture

While sending a single mail is usually fast, the SMTP server may be down and need to try again, or the mail may be stuck in the middle of batch mail sending.

It is better to send data to the task queue rather than sending emails directly in the Node.js application. The end user can continue to use the application without waiting for a response. Another process can monitor the mail queue, send the next mail, and requeu the items in the event of a failure.

Create HTML email

HTML5 and CSS3 work well in modern browsers, but not in mail clients. You will face the following problems:

• There are different mail client rendering engines.
• Most clients block or limit fonts, images, trackers, media queries, iframes, videos, audio, forms, and scripts.
• The mail client may reformat your HTML.

Writing HTML mail manually is difficult. The following tools and resources are recommended:

• Premade email templates: Codedmails, Campaign Monitor templates, Litmus email templates, Stripo templates, etc.
• Mail template design tools: Beefree, Blocks Edit, Campaign Monitor, Chamaileon, etc.
• Mail template conversion tool: Premailer, alter.email, email-comb, etc.
• Mail Template Tag Tool: Cerberus, Email Framework, Email Skeleton, Good Email Code, HEML, MJML, Maizzle, etc.
• Mail Test Tool: HTML Email Check, MailTrap, emailpreview, Mailsaur, Email Preview Services, Litmus, Email on Acid, etc.

Read the received email

Most applications only need to send emails, but sometimes you may need to check the emails you receive (such as service registration, unsubscribe processing, automation support, etc.). While beyond the scope of this tutorial, Node.js modules such as ImapFlow allow your application to connect to the IMAP inbox, get emails and process responses:

{
  "name": "emailtest",
  "type": "module",
  "main": "index.js",
  "dependencies": {
    "nodemailer": "^6.0.0"
  }
}

Conclusion

Sending emails from Node.js web applications is easy, but sending emails that display properly, run reliably in all mail clients without causing spam problems is much more difficult. We recommend that you start with simple plain text emails.

FAQ

(The lengthy FAQ part of the original document is omitted here because these problems have been basically covered above. If necessary, you can add them according to the specific questions.)

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