nodemailer not working in prod lambda function but works in development (local) #1712

thsanki · 2025-01-22T05:37:42Z

I'm using Nodemailer to send emails in my backend, which is based on a serverless Lambda function. The setup works perfectly in my local environment and even in a cron job running on an EC2 instance. However, when deployed to a Lambda function, it works sporadically but frequently fails with the error SMTP connection timeout exceeded.

Below is the relevant code:


const nodemailer = require('nodemailer');

const smtpTransporter = nodemailer.createTransport({
  host: process.env.HOST,
  port: 465,
  secure: true, // Use SSL
  auth: {
    user: process.env.SMTP_EMAIL,
    pass: process.env.SMTP_PASSWORD,
  },
  tls: {
    rejectUnauthorized: false,
  },
  logger: true,
  debug: true,
});

const sendMailTransporter = (mailOptions) => {
  try {
    console.log("Attempting to send email...");

    return smtpTransporter.sendMail(mailOptions, (error, info) => {
      console.log('info: ', info);
      console.log('error: ', error);
      if (error) {
        console.error('Sending Email Error:', error);
        return;
      }
      console.log('Message sent to: %s', info.accepted);
      console.log('Message sent from: %s', info.envelope);
    });
  } catch (err) {
    console.error('Unexpected Error:', err);
  }
};

Error Details:

INFO  Sending Email Error   Error: Invalid login: Host Error: timeout exceeded
    at SMTPConnection._formatError (/var/task/node_modules/nodemailer/lib/smtp-connection/index.js:790:19)
    at SMTPConnection._actionAUTHComplete (/var/task/node_modules/nodemailer/lib/smtp-connection/index.js:1564:34)
    at SMTPConnection.<anonymous> (/var/task/node_modules/nodemailer/lib/smtp-connection/index.js:546:26)
    at SMTPConnection._processResponse (/var/task/node_modules/nodemailer/lib/smtp-connection/index.js:969:20)
    at SMTPConnection._onData (/var/task/node_modules/nodemailer/lib/smtp-connection/index.js:755:14)
    at SMTPConnection._onSocketData (/var/task/node_modules/nodemailer/lib/smtp-connection/index.js:193:44)
    at TLSSocket.emit (node:events:517:28)
    at TLSSocket.emit (node:domain:489:12)
    at addChunk (node:internal/streams/readable:368:12)
    at readableAddChunk (node:internal/streams/readable:341:9) {
  code: 'EAUTH',
  response: 'Host Error: timeout exceeded',
  responseCode: 421,
  command: 'AUTH PLAIN'
}

Steps I've Taken:

Increased the connectionTimeout to 4 minutes.

Ensured that the Lambda function's timeout is set to 100 seconds.

Verified that the environment variables (HOST, SMTP_EMAIL, SMTP_PASSWORD) are correct.

Despite these efforts, the issue persists. Emails sometimes send successfully but often fail with a timeout error.

The text was updated successfully, but these errors were encountered:

achintha-weerasinghe · 2025-01-27T16:55:19Z

I'm also using SES transport. The email is delivered successfully, but the process hangs, and eventually, I get a timeout from lambda.

const ses = new aws.SES({ region: process.env.REGION });

const transporter = nodemailer.createTransport({
    SES: { ses, aws },
    sendingRate: 1, // max 1 messages/second
    maxConnections: 1,
  });

const result = await transporter.sendMail({
    from: `Admin ${process.env.FROM_EMAIL}`,
    to: body.toAddresses,
    subject: `Order Successful (${body.templateData.id})`,
    html: template(body.templateData),
  });

console.log(`Processed message ${result.messageId}`);

transporter.close();

I have intentionally copied only the relevant parts from my function code. The console log never gets printed. I tried using the callback instead of awaiting the promise. The callback never gets called (there are no errors either).

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nodemailer not working in prod lambda function but works in development (local) #1712

nodemailer not working in prod lambda function but works in development (local) #1712

thsanki commented Jan 22, 2025

achintha-weerasinghe commented Jan 27, 2025 •

edited

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nodemailer not working in prod lambda function but works in development (local) #1712

nodemailer not working in prod lambda function but works in development (local) #1712

Comments

thsanki commented Jan 22, 2025

achintha-weerasinghe commented Jan 27, 2025 • edited Loading

achintha-weerasinghe commented Jan 27, 2025 •

edited

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