msglens-cli

Read Outlook .msg, .eml and winmail.dat files from the command line, from Node, or from an AI assistant over MCP. Headers, the message body and attachments, with no Outlook and nothing uploaded.

These are the same parsers that run in the browser at msglens.app.

npx msglens-cli read message.msg

Why another .msg parser

Most real Outlook mail does not store its body as HTML or plain text. In a sample of 20 business .msg files, 17 kept the body only in PidTagRtfCompressed: compressed RTF with the original HTML wrapped inside it (MS-OXRTFCP and MS-OXRTFEX). A parser that reads PidTagHtml and PidTagBody and stops returns an empty body for those messages. This one decompresses the RTF and un-wraps the HTML, falling back through PidTagHtml, PidTagBodyHtml, compressed RTF and PidTagBody in that order.

It also:

• detects the format from the bytes, so a renamed file still opens
• unpacks winmail.dat (TNEF), including the attachments trapped inside it
• decodes non-Latin bodies with the message's declared code page
• reads saved appointments and contacts, not only mail

CLI

Install it with npm install -g msglens-cli and the command is msglens; or run it without installing as npx msglens-cli.

msglens read <file...> [--json]            print headers and the plain-text body
msglens attachments <file...> [-o <dir>]   save every attachment
msglens convert <file...> --to eml|txt [-o <dir>]
msglens mcp                                MCP server on stdio (see below)

• read --json prints the full parsed message (one object for one file, an array for several). Attachment bytes are left out; names, types and sizes stay.
• attachments and convert never overwrite: a second invoice.pdf is saved as invoice (1).pdf. Attachment names are reduced to a plain file name, so a message cannot write outside the output folder.
• Several files at once work, and a file that fails is reported without stopping the rest. The exit code is 1 if any file failed.

Convert a folder of .msg files to .eml:

npx msglens-cli convert ./mail/*.msg --to eml -o ./eml

MCP server for AI assistants

msglens mcp runs a Model Context Protocol server on stdio, so Claude, Codex, Cursor and other assistants can open email files on your machine themselves. It has three tools:

• read_email: subject, sender, recipients, date, plain-text body and the attachment list (optionally the raw headers)
• save_attachments: writes every attachment into a folder
• convert_email: .msg or winmail.dat to .eml or .txt

The files stay on your machine; the server makes no network requests.

Claude Code

claude mcp add msglens -- npx -y msglens-cli mcp

Codex (~/.codex/config.toml)

[mcp_servers.msglens]
command = "npx"
args = ["-y", "msglens-cli", "mcp"]

Claude Desktop, Cursor and other JSON-configured clients

{
  "mcpServers": {
    "msglens": { "command": "npx", "args": ["-y", "msglens-cli", "mcp"] }
  }
}

Then ask, for example, "summarise ~/Downloads/invoice-query.msg and save its attachments to ~/Desktop/invoice".

Message text is written by whoever sent the email, so the tools tell the assistant to treat it as data and not to follow instructions inside it.

Library

import { parseFile, parse, toEml, toText } from "msglens-cli";

const email = await parseFile("message.msg");
email.subject;          // string
email.from;             // { name, address } | null
email.date;             // Date | null
email.bodyText;         // plain text, always filled
email.body;             // HTML when email.bodyKind === "html"
email.attachments;      // [{ fileName, mimeType, size, content: Uint8Array, isEmbeddedMessage, ... }]

const again = await parse(bytes, "message.msg"); // from a Uint8Array or ArrayBuffer
const eml = await toEml(email);                   // RFC 822 text

email.body is the message's HTML exactly as the sender wrote it. It is untrusted: sanitise it (for example with DOMPurify) before rendering it anywhere.

An attachment with isEmbeddedMessage: true is a message attached to a message; pass its content to parse() to read it.

Requires Node 20 or later.

Want to just look at a file?

msglens.app opens .msg, .eml and winmail.dat in the browser, parsed on your device, with attachments and PDF export.

Licence

MIT. Microsoft and Outlook are trademarks of Microsoft Corporation; this project is not affiliated with Microsoft.