Error: nodemailer Missing Credentials for Plain

What's Causing This Error?

This error occurs on Node.js applications deployed on Heroku without proper configuration of environment variables. Additionally, you may also run into this error due to invalid configurations.

Solution - Here's How To Resolve It

Resolving the error by updating configurations

Ensure that you have configured Nodemailer successfully. You may use the snippet shown below as a guide for configuring Nodemailer.

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const transporter = nodemailer.createTransport({
    service: 'gmail', // or your own SMTP 
    providerauth: {user: 'your-gmail@gmail.com'}, // user -> important
    pass: 'your-password' // pass -> important (do not use password)
});

const mailOptions = {
    from: 'SENDER-EMAIL',
    to: 'RECIPIENT-EMAIL',
    subject: 'SUBJECT',
    text: 'EMAIL BODY',
};
transporter.sendMail(mailOptions,(err,res)=>{
    if(err){
        console.log(err);
    }
    else {
        console.log('The email was sent successfully');
    }
});

Additionally, if you are using Google SMTP servers, ensure that you have turned on Less Secure Sign In. For users that use Office 365, ensure that SMTP authentication is turned on for your Microsoft account.

Resolving the error in Heroku

You will need to configure your Nodemailer environment variables in the deployed Heroku application.

To do so, first, log in to your Heroku console. Afterward, click on the deployed application and click "Settings." You will see the output shown below.

Figure 01 - Heroku application settings

Hereafter, click on "Reveal Config Vars." It will display the output shown below.

Figure 02 - Viewing config variables in the Heroku console

Then, add the environment variables that you use with Nodemailer.

Figure 03 - Adding config variables to Heroku

Finally, re-rerun the application to see the emails getting sent successfully!

Resolving steps if none of the above works

If none of the actions work for you, ensure that you have provided the correct username/password, port, and protocol. Additionally, if you use dotenv to load the environment file, ensure that you properly access the configurations.

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// add this snippet to the top of your Node.js file to initialize the .env file that you have created to store the env variables.
const dotenv = require('dotenv');
dotenv.config();

// access env
console.log(process.env.NODE_MAILER_USERNAME);