Attachments 📎

Want to send a PDF receipt? An image? A spreadsheet? No problem. You can attach basically any file to any email you send through Mailofly.

How it works

Attachments go inside the attachments array in your request. Each file needs a name and its content (encoded in base64 — more on that in a sec). Here’s what each attachment object looks like:

Field	What it is
`filename`	The name that shows up in the email (e.g. `invoice.pdf`)
`content`	The file, converted to a base64 string
`content_type`	Optional. The MIME type like `application/pdf` or `image/png`
`disposition`	Optional. `"attachment"` (default) or `"inline"` (embed in email body)
`content_id`	Optional. Used when you want to embed images inline with a `cid:` reference

Example: Attaching a PDF invoice

import { Mailofly } from "@mailofly/node";
import * as fs from "fs";

const mailofly = new Mailofly("mfly_live_your_api_key");

// Read the file and convert it to base64
const pdfBuffer = fs.readFileSync("./invoice-101.pdf");
const base64Pdf = pdfBuffer.toString("base64");

await mailofly.emails.send({
  from: "Billing <billing@yourcompany.com>",
  to: ["customer@example.com"],
  subject: "Here's your receipt 🧾",
  html: "<p>Hi! Your receipt is attached below. Thanks for your purchase!</p>",
  attachments: [
    {
      filename: "invoice-101.pdf",
      content: base64Pdf,
      content_type: "application/pdf",
    },
  ],
});

Example: Inline images (embed inside email)

Sometimes you want an image to appear inside the email, not as a separate download. Use disposition: "inline" and give it a content_id, then reference it in your HTML with cid::

await mailofly.emails.send({
  from: "Acme <marketing@acme.com>",
  to: ["user@example.com"],
  subject: "You earned a badge! 🏅",
  html: `<p>Congrats! Here's your badge:</p><img src="cid:badge_image" alt="Your Badge" />`,
  attachments: [
    {
      filename: "badge.png",
      content: fs.readFileSync("./badge.png").toString("base64"),
      content_type: "image/png",
      disposition: "inline",
      content_id: "badge_image",
    },
  ],
});

Limits to keep in mind

📦 Max email size: 25 MB total — that includes HTML, headers, and all attachments combined.
🚫 Blocked file types: Executables like .exe, .bat, .cmd, .scr, .vbs, .js are rejected automatically. This protects your recipients and keeps spam filters happy.