How to use a pino logger instance on nodemailer

Nodemailer has debug options available in order to log transaction events and SMTP traffic messages, these options are "logger" which can receive a boolean true or false, if this option is set to true then transaction events are printed on console, this option can also receive a logger instance which needs to be bunyan compatible. The other option is "debug" which can receive a boolean true or false, if this option is set to true then SMTP traffic messages are printed

First we need to create a new folder an initialize a node project

mkdir NodemailerPinoLogger
cd NodemailerPinoLogger
npm init -y

This is a list of all the packages needed and the reason why we will install them:

"express" (npm install express): Simplifies the creation of RESTful APIs
using Node

"pino" (npm install pino): Logging framework for Node.js
using Node

"nodemailer" (npm install nodemailer): is a module for Node.js applications to allow email sending
using Node

Now we will create our express server so we could test a nodemailer instance using pino logger, first create an app.js file

// ./app.js

// Import express
const express = require("express");
// Import pino and create logger instance
const logger = require('pino')()
// Import nodemailer
const nodemailer = require("nodemailer");

// Create nodemailer transport
const transporter = nodemailer.createTransport({
    // Use your own SMPT host
    host: "",
    port: 465,
    secure: true, // Use `true` for port 465, `false` for all other ports
    // Use your auth credentials for the SMTP server
    auth: {
        user: "",
        pass: "",
    },
    // Pass pino logger instance to transport logger option
    logger,
    // Set debug option to true
    debug: true,

});

const app = express();

app.use(express.json());

// Route to check server is working
app.get("/", (req, res) => {
    logger.info("logger working")
    res.status(200).send('Working');
})

// Route used to send email and test logger
app.get("/send-email", async (req, res) => {
    // Use created transport to send email
    logger.info("logger working")
    transporter.sendMail({
        from: 'jhony.gutidiaz@gmail.com', // sender address
        to: "oliverbravo45@gmail.com", // list of receivers
        subject: "Test email", // Subject line
        text: "Test message", // plain text body
    });
    res.status(200).send('Email sent');
})

module.exports = app;

now create a new file called index.js on the base of the project. We will use the app from above to listen for new requests

// ./index.js

const app = require("./app");

// Port that will be uses to listen to requests
const port = process.env.PORT || 3015;

/**
 * Listen on port 3015
 */
app.listen(port, () => {
    console.log(`App listening on port ${port}!`);
});

now if you passed correct SMTP credentials and go to the following endpoint http://localhost:3015/send-email you will see on the console nodemailer transaction events and SMTP traffic messages, moments after you should receive the test email

In this repository https://github.com/obravocedillo/NodemailerPinoLogger you can find the code implementing all the solutions mentioned.