Sendmail transport

The Sendmail transport delivers email by passing the generated RFC 822 message to the local sendmail command (or a compatible mail transfer agent such as Postfix or Exim). The message is piped directly to the program's standard input. This is the same mechanism used by PHP's mail() function.

Usage

// CommonJS
const nodemailer = require("nodemailer");

const transporter = nodemailer.createTransport({
  sendmail: true, // enable Sendmail transport
});

Setting sendmail: true activates the Sendmail transport. Nodemailer looks for a sendmail executable in your system's PATH by default. If your sendmail binary is located elsewhere, you can specify the full path using the path option described below.

Transport options

Option	Type	Default	Description
path	String	'sendmail'	Path to the sendmail binary. Can be an absolute path (e.g., /usr/sbin/sendmail) or just the executable name if it is in your PATH.
newline	'unix' / 'windows'	'unix'	Line ending style for the generated message. Use 'unix' for \n (LF) or 'windows' for \r\n (CRLF). Most systems work fine with the default 'unix' setting.
args	String[]	none	Custom command-line arguments for the sendmail binary. When you provide this array, it replaces Nodemailer's default arguments except for -i (which is always included) and the recipient addresses (which are always appended). See the examples below for common use cases.

When no custom args array is provided, Nodemailer executes the following command:

sendmail -i -f <from> <to...>

When you provide a custom args array, the command becomes:

sendmail -i <args...> <to...>

Note that the -i flag (which prevents a single dot on a line from being treated as the end of the message) and the recipient list are always included automatically.

Response

After successfully sending a message, transporter.sendMail() resolves with an info object containing the following properties:

• envelope - An object with from (string) and to (array of strings) properties representing the message envelope
• messageId - The generated Message-ID header value for the sent message
• response - The string 'Messages queued for delivery'

Note that the sendmail command does not produce output, so the response is a static confirmation message from Nodemailer.

Troubleshooting

If Nodemailer cannot find the sendmail binary, you will receive an error with exit code 127. To resolve this:

1. Verify that sendmail (or a compatible MTA like Postfix) is installed on your system
2. Check that the binary is accessible via your PATH, or specify the full path using the path option
3. Common locations include /usr/sbin/sendmail and /usr/lib/sendmail

For installation instructions, consult your operating system's documentation or the Computer Hope sendmail reference.

Examples

Specifying a custom binary path

Use the path option when the sendmail binary is not in your PATH or you want to use a specific location:

const nodemailer = require("nodemailer");

const transporter = nodemailer.createTransport({
  sendmail: true,
  newline: "unix",
  path: "/usr/sbin/sendmail",
});

transporter.sendMail(
  {
    from: "sender@example.com",
    to: "recipient@example.com",
    subject: "Test message",
    text: "I hope this message gets delivered!",
  },
  (err, info) => {
    if (err) {
      console.error(err);
      return;
    }
    console.log(info.envelope);
    console.log(info.messageId);
  }
);

Passing custom command-line arguments

Use the args option to pass additional flags to the sendmail binary. For example, to override the envelope sender address (useful for setting a custom bounce address):

const transporter = nodemailer.createTransport({
  sendmail: true,
  args: ["-f", "bounce@example.com"],
});

When using args, remember that you are replacing Nodemailer's default arguments. If you need the -f flag for the envelope sender, you must include it explicitly as shown above.