Make sure you setup a project on the Google Developers Page using the account from which you want to send email.

See the following link describing the process of obtaining the required authorization tokens for nodemailer.

Extract of important steps

Step 1 : Installation

npm install nodemailer

Step 2 : Register your Application at Google APIs Console

XOAuth2 is similar with OAuth2, so you need to register your application to Google. Jump to Google APIs Console, then create a project if you don’t have, and open “API Access” page.

In this here, when you create a client ID, put “https://developers.google.com/oauthplayground” into the text box for Redirect URIs.

Step 3 : Open Google OAuth2.0 Playground.

You will obtain refreshToken & accessToken on this step at Google OAuth2.0 Playground. Open the page from https://developers.google.com/oauthplayground, then click the gear button on the right-top.

Set your client ID & client secret that obtained on step2, and select “Access token location:” as “Authorization header w/ Bearer prefix”. Then close it.

And set up the scopes. Put “https://mail.google.com/” into the textbox below the service scope list.

Then click [Authorize APIs] button.

Step 4 : Obtain the “refresh token”.

After OAuth2.0 authorization, click [Exchange authorization code for tokens] button. You can get your refresh token.

Use the following javascript template:

    var nodemailer = require("nodemailer");

    var smtpTransport = nodemailer.createTransport("SMTP", {
      service: "Gmail",
      auth: {
        XOAuth2: {
          user: "[email protected]", // Your gmail address.
                                                // Not @developer.gserviceaccount.com
          clientId: "your_client_id",
          clientSecret: "your_client_secret",
          refreshToken: "your_refresh_token"
        }
      }
    });

    var mailOptions = {
      from: "[email protected]",
      to: "[email protected]",
      subject: "Hello",
      generateTextFromHTML: true,
      html: "<b data-preserve-html-node="true">Hello world</b>"
    };

    smtpTransport.sendMail(mailOptions, function(error, response) {
      if (error) {
        console.log(error);
      } else {
        console.log(response);
      }
      smtpTransport.close();
    });