So I have this one problem with an app I am building using Nodemailer to send email to an SMTP server (or gmail) and I am getting a weird problem.

TL;DR: The email does get sent but it’s rare. Other times it just hangs at Resolved then eventually times out (I added a time out).

Here is a video of what the console is doing: Here

As you can see in the video, eventually the email gets sent. Then it times out.

I get an ‘ETIMEDOUT’ error on most of the times it attempts to send.

Not that it’s needed but I’m sending an email by pushing a button on a site built with ReactJS. I also tried directly accessing the API function using Thunder Client. That has nothing to do with it.

Here is the transporter:
`// Define which service to use
// gmail = Use gmail’s service (must have GmailSMTPUser and GmailSMTPAppPass setup)
// ll = Use LumiereLabs’s service
const emailService = serviceSettings.use
// Configure the transporter

switch (emailService) {
    case "gmail":
        return nodemailer.createTransport({
            service: 'gmail',
            auth: {
                user: serviceSettings.services.gmail.user,
                pass: serviceSettings.services.gmail.pass
            },
            logger: true,
            debug: true,
            maxConnections: 5, // Maximum number of connections to keep in the pool
            maxMessages: 100, // Maximum number of messages to send per connection
            rateLimit: 10, // Maximum number of messages to send per second
            pool: true, // disable connection pooling
            connectionTimeout: 10000,  // 10 seconds
            socketTimeout: 10000,      // 10 seconds
            greetingTimeout: 5000      // 5 seconds    
        })
    break

    case "ll":
        return nodemailer.createTransport({                    
            host: 'smtp.lumierelabs.org',
            port: 587,
            secure: false,       // true for 465, false for others
            requireTLS: true,
            auth: {
                user: serviceSettings.services.ll.user,
                pass: serviceSettings.services.ll.pass
            },
            tls: {
                rejectUnauthorized: false // if using self-signed certificates
            },
            logger: true,
            debug: true,
            maxConnections: 5, // Maximum number of connections to keep in the pool
            maxMessages: 100, // Maximum number of messages to send per connection
            rateLimit: 10, // Maximum number of messages to send per second
            pool: true, // disable connection pooling
            connectionTimeout: 10000,  // 10 seconds
            socketTimeout: 10000,      // 10 seconds
            greetingTimeout: 5000      // 5 seconds                
        })
    break
}`

Here is the function I created to handle the email:
`const sendEmail = async (mailOptions, successMessage, res, serviceSettings) => {
let toasts = []

const transporter = createTransporter(serviceSettings)
            
try {
    let info = await transporter.sendMail(mailOptions)

    // Send to notification
    toasts.push({ message: successMessage, object: { sentEmail: true }, type: 'success' })

    // Send to console
    console.log('Email sent: ' + info.response)
} catch (error) {
    // Send to notification
    toasts.push({ message: `Error sending mail: ${error}`, object: { sentEmail: false },  type: 'error'})

    // Send to console
    console.error('Error sending email: ', error)

    // Rethrow error to handle it upstream
    throw error
} finally {
    transporter.close() // close the connection pool

    // return something
    if(toasts.length > 0) {
        // Toasts found!
        // Check for type
        if (toasts[0].type === "error") {                                               
            // Error                                                                        
            if (!res.headersSent) {
                return res.status(400).json(toasts)
            } else {
                console.warn('Attempted to send a response after headers were already sent.');
            }                      
        } if (toasts[0].type === "unauthorized") {
            // Unauthorized
            if (!res.headersSent) {
                return res.status(401).json(toasts)
            } else {
                console.warn('Attempted to send a response after headers were already sent.');
            }                      
        } else {
            if (!res.headersSent) {
                return res.status(200).json(toasts)
            } else {
                console.warn('Attempted to send a response after headers were already sent.');
            }                      
        }
    }
}

}`

The function is called from a userController.js on a express JS backend:
await sendEmail(mailOptions, successMessage, res, serviceSettings)

Node Version: 22.2.0
NPM Version: 10.7.0
Development Operating System: Windows 11
SMTP Server OS: Ubuntu 22.04 using Postfix and Dovecot

Any help would be greatly appreciated.

What have I done to mitigate this?

1. Changed from a self-hosted SMTP server (smtp.lumierelabs.org) to a gmail service. Same result. So it’s not an SMTP problem.

2. Created a separate app aside from the project that has the nodemailer and still got the result.

3. Restarted computer. Same result.

4. Checked telnet of smtp.lumierelabs.org on Command Prompt, smtp server works. So I know it’s not an SMTP problem.

5. Re-installed nodemailer

6. Googled the problem and can’t find something similiar.

7. Turned off Windows Defender Firewall, no change.