Hey there! Let's break this down for you step by step—since it's totally normal to mix up these concepts when you're new to SMTP.

First: Clarifying the Key Concepts #

Let's get the confusion out of the way first—these two are completely separate things:

• SMTP Server Authentication: This is about verifying you have permission to use the server to send emails (to cut down on spam/abuse). It has nothing to do with encrypting your email content.
• Email Encryption (TLS/SSL): This encrypts the transmission of your email between your client and the SMTP server, so no one can snoop on the content while it's in transit.

The short answer: Yes, you absolutely can send encrypted emails without SMTP authentication—if your SMTP server supports it. Some servers (like internal corporate servers or trusted open relays) allow unauthenticated connections but require encryption for security.

Fixing Your Nodemailer Configuration #

The issue with your current code is likely how you're enabling encryption. Let's adjust it based on how your server handles secure connections:

Case 1: Your server uses STARTTLS (port 587) #

Most modern servers use STARTTLS, which starts with a plaintext connection then upgrades to TLS encryption. For this setup, use requireTLS: true instead of secure: true:

let transporter = nodemailer.createTransport({
  host: prop.mailHost,
  port: prop.mailPort, // Make sure this is set to 587 for STARTTLS
  secure: false, // Don't use direct SSL here
  requireTLS: true, // Force the connection to upgrade to TLS encryption
  // No auth object needed since we don't require server authentication
});

transporter.sendMail(mailOptions, function(error, info) {
  if (error) {
    return console.log(error);
  }
  console.log("successfully sent mail");
});

Case 2: Your server uses direct SSL (port 465) #

If your server uses SSL encryption from the very start (usually port 465), secure: true is correct—but you need to confirm two things:

1. Your server actually allows unauthenticated connections over SSL.
2. You've set the correct port (465) in your config.

If this still fails, check the error message Nodemailer throws—it might tell you the server doesn't support unauthenticated SSL, or there's a certificate issue. (You can add tls: { rejectUnauthorized: false } temporarily to test, but don't leave this in production unless you fully trust the server.)

Troubleshooting Tips #

• Double-check your server's docs: Confirm which encryption method (STARTTLS vs SSL) it supports, and if unauthenticated encrypted connections are allowed.
• Read the error output: Nodemailer's error messages are usually specific—they might say "server requires authentication" or "STARTTLS not supported".
• Test with command-line tools first: Run openssl s_client -connect your-host:587 -starttls smtp to see if the server accepts STARTTLS connections without auth.

Alternative Node.js Packages #

If Nodemailer isn't working out for you, here are other options that support encryption and attachments:

• emailjs: A lightweight SMTP client with a simple API. It works with unauthenticated servers (if allowed) and supports TLS/SSL and attachments.
• sendmail: If your server has a local sendmail service installed, this package calls it directly. It supports encryption and attachments, and often works without explicit SMTP auth if the sendmail config allows it.
• mailgun-js: If you're open to a hosted solution instead of your own SMTP server, Mailgun handles encrypted connections and authentication for you—great if you don't want to manage server settings.

内容的提问来源于stack exchange，提问作者Hari Ram