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Sometimes you already have a fully-formatted RFC 822/EML message ready to send. This might happen when a message was composed by another system, retrieved from storage, parsed from an EML file using MailParser, or generated with Mailcomposer. In these cases, you can pass the pre-built content directly to Nodemailer using the raw option, and Nodemailer will send it without modifying the structure.

The raw option can be used at three different levels:

  1. Whole message - Provide a complete RFC 822 document including all headers and body content.
  2. Per alternative - Provide a pre-built MIME part for text/plain, text/html, or any other alternative content type.
  3. Per attachment - Provide a complete attachment including its MIME headers and body.

At each level, raw accepts the same source forms as attachment content: a string, a Buffer, a readable stream, { path: "/path/to/message.eml" }, or { href: "https://example.com/message.eml" }.

Always set an envelope

When you use raw for the entire message, you must also provide envelope.from and envelope.to explicitly. Nodemailer does not parse these values from the raw message content. The envelope tells the SMTP server who the sender and recipients are during the mail transfer.

Examples​

1. String as the entire message​

const message = {
  envelope: {
    from: "sender@example.com",
    to: ["recipient@example.com"],
  },
  raw: `From: sender@example.com
To: recipient@example.com
Subject: Hello world

Hello world!`,
};

Newlines in raw content are kept as-is when the message is generated. The SMTP transport normalizes bare \n to \r\n automatically while transmitting the message, but other transports (stream, SES) emit the content unchanged — set the message option newline: 'windows' if you need guaranteed CRLF output there.

2. EML file as the entire message​

You can read the message content from a file on disk by providing a path property instead of a string.

const message = {
  envelope: {
    from: "sender@example.com",
    to: ["recipient@example.com"],
  },
  raw: {
    path: "/path/to/message.eml",
  },
};

The path can be absolute or relative to the current working directory (process.cwd()).

3. String as an attachment​

When using raw inside the attachments array, you must include all of the MIME headers yourself. Nodemailer does not add Content-Type, Content-Disposition, or any other headers automatically.

const message = {
  from: "sender@example.com",
  to: "recipient@example.com",
  subject: "Custom attachment",
  attachments: [
    {
      raw: `Content-Type: text/plain
Content-Disposition: attachment; filename="notes.txt"

Attached text file`,
    },
  ],
};