Attachments

Use the attachments option of the message object to attach files.

An attachment is an object inside the attachments array. You can attach as many files as you need.

Property	Type	Description
filename	string	Name that will be displayed to the recipient. Unicode is allowed.
content	string | Buffer | Stream	Contents of the file.
path	string	Filesystem path or URL (including data URIs). Nodemailer streams the file instead of reading it fully into memory—recommended for large files.
href	string	HTTP(S) URL that Nodemailer should fetch and attach.
httpHeaders	object	Custom HTTP headers for href, for example { authorization: 'Bearer …' }.
contentType	string	Explicit MIME type. Defaults to the type inferred from filename.
contentDisposition	string	Content‑Disposition header. Defaults to 'attachment'.
cid	string	Content‑ID for embedding the attachment inline in the HTML body (<img src="cid:my-logo"/>).
encoding	string	Encoding applied when content is a string (e.g. 'base64', 'hex').
headers	object	Custom headers for the individual MIME node.
raw	string	Advanced: Full pre‑built MIME node including headers. Overrides every other field.

Streaming vs. in‑memory

Prefer path, href, or a Stream when attaching large files so that Nodemailer can stream data without loading it all into memory.

Examples

const fs = require("fs");

// inside a message object
attachments: [
  // 1. Plain text
  {
    filename: "hello.txt",
    content: "Hello world!",
  },

  // 2. Binary (Buffer)
  {
    filename: "buffer.txt",
    content: Buffer.from("Hello world!", "utf8"),
  },

  // 3. Local file (streamed)
  {
    filename: "report.pdf",
    path: "/absolute/path/to/report.pdf",
  },

  // 4. Implicit filename & type (derived from path)
  {
    path: "/absolute/path/to/image.png",
  },

  // 5. Readable stream
  {
    filename: "notes.txt",
    content: fs.createReadStream("./notes.txt"),
  },

  // 6. Custom content‑type
  {
    filename: "data.bin",
    content: Buffer.from("deadbeef", "hex"),
    contentType: "application/octet-stream",
  },

  // 7. Remote file
  {
    filename: "license.txt",
    href: "https://raw.githubusercontent.com/nodemailer/nodemailer/master/LICENSE",
  },

  // 8. Base64‑encoded string
  {
    filename: "photo.jpg",
    content: "/9j/4AAQSkZJRgABAQAAAQABAAD…", // truncated
    encoding: "base64",
  },

  // 9. Data URI
  {
    path: "data:text/plain;base64,SGVsbG8gd29ybGQ=",
  },

  // 10. Pre‑built MIME node
  {
    raw: ["Content-Type: text/plain; charset=utf-8", 'Content-Disposition: attachment; filename="greeting.txt"', "", "Hello world!"].join("\r\n"),
  },
];

Embedding images

To embed an image inside the HTML part of the email, set a cid on the attachment and reference that CID in the HTML:

attachments: [
  {
    filename: 'logo.png',
    path: './assets/logo.png',
    cid: 'logo@nodemailer'
  }
],
html: '<p><img src="cid:logo@nodemailer" alt="Nodemailer logo"></p>'