Setup gmail OAuth2 with nodemailer.

• go to google cloud console
• search for api and service
• crete new project
• then go to credentials
• create new Outh client ID under create new credentiala. (you may need to setup OAuth consent screen to be able to create new credentials).
• on creating new crendentials choose web application as type.
• set Authorize redirect as :

    https://developers.google.com/oauthplayground

• then copy the given client_id and client_secret.

on outhplayground website.

• on setting (gear wheel) icon, click it and enable use your own Outh credentials
• fill in the client_id and client_secret you copied earlier and hit close.
• on left side where it says select and Authorize API. paste this : https://mail.google.com.
• then click authorize api.
• a new tab will redirect to your google login page.
• login to your account (amil sender). and approve the API.
• click : Exchange authorization code for tokens and then copy the refresh token.
• we are now ready to write our code.

In Node.js.

• install nodemailer.
• install googleapis using : npm install googleapis.
• crate new mailing service. (I usually create it under path: lib/mailer.js
• inside that file import googleapis and nodemailer.

const mailer = require('nodemailer');
const {google} = require('googleapis');

• create new oAuth2 client by passing our client_id, client_secret and our Authorize redirect address, which is.

https://developers.google.com/oauthplayground

const oAuth2Client = new google.Auth.OAuth2(
	`REPLACE_THIS_WITH_OUR_CLIENT_ID`,
	`REPLACE_THIS_WITH_OUR_CLIENT_SECRET',
	`REPLACE_THIS_WITH_OUR_AUTH_REDIRECT`,
);

• then set our refresh token to out OAuth2Client by passing the refresh token we copied earlier.

oAuth2Client.setCredentials(REPLACE_THIS_WITH_OUR_RF_TOKEN);

• then we can get the accessToken to our emailservice from the OAuth2Client.

const accessToken = oAuth2Client.getAccessToken();

• using that accessToken, we can send mail using nodemailer by setting the Auth type options to OAuth2.
• example nodemailer transporter.

const transporter = nodemailer.createTransport({
	service: 'gmail',
	auth : {
		type: 'OAuth2',
		user: 'sendergmailaddress@gmail.com',
		clientId: 'REPLACE_THIS_WITH_OUR_CLIENT_ID_COPIED_EARLIER',
		clientSecret: 'REPLACE_THIS_WITH_OUR_CLIENT_SECRET',
		accessToken,
	},
});