M365 Attachment Reader MCP Local

A local stdio MCP server for Claude Desktop that reads Outlook emails and deeply parses email attachments through the Microsoft Graph API.

Status: Functional for personal single-user local use with Claude Desktop.

---

Why This Exists

Claude's built-in Microsoft 365 connector can list emails, read message bodies, and check calendars. But it cannot read the actual content inside email attachments.

That means when you say "What does the PDF in my latest email say?", Claude can see the attachment metadata, but not the text, tables, images, or nested documents inside it.

This project fills that gap — running entirely on your local machine over stdio, with no public endpoints or tunnels required.

---

What It Does

This server runs as a local MCP process started by Claude Desktop. It:

1. Authenticates with Microsoft 365 via device code flow
2. Lists Outlook emails and their attachments through Microsoft Graph
3. Downloads and parses attachment contents locally
4. Returns structured text and image blocks directly to Claude Desktop

Supported Formats

Format	What Gets Extracted
PDF	Full text content
Scanned PDF	OCR text, plus optional rendered page images
DOCX	Text and embedded images
DOC	Text content
PPTX / PPTM / PPSX / POTX	Slide text, notes, and embedded images
PPT	Best-effort legacy text extraction
XLSX / XLS / CSV	All sheets converted to CSV
JPG / JPEG / PNG / GIF / WEBP / BMP / TIFF	Returned as MCP image blocks for visual analysis
ZIP / RAR / 7Z	Archive contents recursively parsed file by file
MSG	Subject, sender, body, and embedded attachments
TXT / MD / JSON / XML / HTML	Raw text
Outlook itemAttachment	Text content

MCP Tools

Tool	Description
health_check	Check if the server is alive
begin_auth	Start device code login flow
auth_status	Check authentication status
list_recent_messages	List recent Outlook emails
list_email_attachments	List attachments for a specific email
read_email_attachment	Download, parse, and return attachment content

---

Real-World Use Cases

Retail / Sales Operations

"Pull the last 5 Daily Dashboard emails, read the Excel attachments, and analyze the sales trend across all store locations over the past week."

Finance / Accounting

"Find the latest email from our vendor with 'Invoice' in the subject, read the PDF attachment, and extract the total amount, due date, and line items."

Legal / Contract Review

"Open the most recent email from legal@partner.com, read the Word or PowerPoint attachment, and summarize the key terms."

HR / Recruiting

"Find emails from recruiting@company.com with attachments, read each resume PDF, and create a comparison table of candidates."

---

Prerequisites

• Windows 10/11, macOS, or Linux
• Node.js 20 or later
• Claude Desktop
• A Microsoft 365 / Outlook account
• A Microsoft Entra app registration (see Step 1 below)

---

Setup

1. Create a Microsoft Entra App Registration

Go to Microsoft Entra admin center → App registrations → New registration.

• Name: anything you like, e.g. m365-mcp-local
• Supported account types: Accounts in any organizational directory and personal Microsoft accounts

Then:

1. Copy the Application (client) ID from the Overview page
2. Go to Authentication → enable Allow public client flows → Save
3. Go to API permissions → Add a permission → Microsoft Graph → Delegated permissions → add User.Read and Mail.Read → Grant admin consent
4. Go to Manifest → find requestedAccessTokenVersion (it may be nested inside api) → set it to 2 → Save

Why step 4? When your app supports personal Microsoft accounts, Microsoft Entra requires access tokens to be v2. The portal doesn't always set this automatically, and the common endpoint will fail with AADSTS50059 if the token version is still null or 1. If you skip this step you will get invalid_grant errors during begin_auth.

Using v1 API integrations? Only set this to 2 if all your Graph/API permissions support v2 tokens (all Microsoft Graph delegated permissions do). If you're integrating custom APIs that only accept v1 tokens, use M365_TENANT_ID=consumers (personal accounts only) or a specific tenant ID instead of common, and leave requestedAccessTokenVersion at its default.

2. Clone and Install

git clone https://github.com/Zacccck/Claude-MCP-Read-Email-Attachments.git
cd Claude-MCP-Read-Email-Attachments
npm install

3. Configure Environment Variables

Copy the example file:

cp .env.example .env

Edit .env and fill in your client ID:

M365_CLIENT_ID=your-application-client-id-here
M365_TENANT_ID=common
M365_AUTO_OPEN_BROWSER=true

Variable reference:

Variable	Required	Description
M365_CLIENT_ID	✅ Yes	Your Entra app's Application (client) ID
M365_TENANT_ID	No	Default common works for most accounts
M365_AUTO_OPEN_BROWSER	No	Set true to auto-open Microsoft login page
M365_MCP_DATA_DIR	No	Custom path for auth cache; auto-detected if omitted

4. Find Your Node.js Path

You'll need the full path to node.exe (Windows) or node (macOS/Linux) in the next step.

# Windows
where.exe node

# macOS / Linux
which node

Example output: C:\Program Files\nodejs\node.exe

5. Open Claude Desktop's Config File

Locate and open the config file for your platform:

Platform	Path
Windows (standard)	%APPDATA%\Claude\claude_desktop_config.json
Windows (Store)	%LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\claude_desktop_config.json
macOS	~/Library/Application Support/Claude/claude_desktop_config.json

If the file does not exist yet, create it.

6. Add the Server to Claude Desktop

Add the following entry to claude_desktop_config.json:

{
  "mcpServers": {
    "m365-attachment-reader-local": {
      "command": "C:\\Program Files\\nodejs\\node.exe",
      "args": [
        "C:\\path\\to\\Claude-MCP-Read-Email-Attachments\\server.mjs"
      ],
      "env": {
        "M365_CLIENT_ID": "your-client-id",
        "M365_TENANT_ID": "common",
        "M365_AUTO_OPEN_BROWSER": "true"
      }
    }
  }
}

Tips:

• Use the full absolute path from Step 4 for command.
• Replace args[0] with the actual path to server.mjs on your machine.
• If you already have other MCP servers in the config, merge this entry into the existing mcpServers object — do not overwrite the whole file.

7. Restart Claude Desktop

Completely quit Claude Desktop and reopen it. Claude Desktop starts the MCP server automatically — you do not need to run node server.mjs manually.

8. Authenticate with Microsoft 365

In Claude Desktop, type:

Please call begin_auth

A browser window will open (or you'll receive a login URL + device code). Complete the Microsoft login flow, then verify:

Please call auth_status

You should see your Microsoft account listed as authenticated.

9. Verify It Works

Run a quick health check:

Please call health_check

Then try a real request:

Show me my recent Outlook emails with attachments

Summarize the contents of the attachments from the latest email

---

Suggested Claude Prompts

Please call begin_auth

Please call auth_status

Show me my recent Outlook emails with attachments

Summarize the contents of the attachments from the email

Find the latest invoice email and extract the total amount, due date, and line items from the PDF attachment

---

Troubleshooting

Problem	Solution
Claude cannot find MCP tools	Restart Claude Desktop completely. Check that command and args paths in the config are correct and absolute.
invalid_grant error with empty userCode in logs	Almost always a token-version or account-type mismatch on the Entra app. See the next two rows.
AADSTS50059: No tenant-identifying information found	Your app does not support the common endpoint. Open the Entra app → Authentication → set Supported account types to Accounts in any organizational directory and personal Microsoft accounts, then save.
Property api.requestedAccessTokenVersion is invalid when saving account types	Open the Entra app → Manifest → set requestedAccessTokenVersion to 2 → save. Then retry changing the account type.
Device code not showing	Make sure begin_auth was called successfully. Do not manually enter a code.
Want to switch Microsoft accounts	Restart Claude Desktop and call begin_auth again in a private browser window.
Debug log location	<M365_MCP_DATA_DIR>\debug.log — defaults to a subdirectory auto-created next to server.mjs.

---

Manual Development Run

For debugging outside Claude Desktop, start the server manually:

cd Claude-MCP-Read-Email-Attachments
node .\server.mjs

Note: Do not type into that terminal. It is a stdio MCP process and expects an MCP client on standard input/output.

---

Docker

A Dockerfile is included for containerized testing:

docker build -t m365-attachment-reader-mcp-local .
docker run --rm -i `
  -e M365_CLIENT_ID=your-client-id `
  -e M365_TENANT_ID=common `
  -e M365_AUTO_OPEN_BROWSER=false `
  m365-attachment-reader-mcp-local

The container still runs as a stdio server. For everyday Claude Desktop use, the direct node approach in Step 6 is simpler.

---

Project Structure

Claude-MCP-Read-Email-Attachments/
├── server.mjs
├── package.json
├── manifest.json
├── server.json
├── glama.json
├── Dockerfile
├── .env.example
├── .gitignore
├── LICENSE
└── README.md

---

Limitations

• Single-user only — one server instance supports one Microsoft account at a time
• Auth state is in-memory — restarting the server requires re-authenticating
• You must create your own Entra app and supply your own client ID
• Very large images may be downscaled or skipped to stay within Claude Desktop payload limits
• Legacy .xls parsing is best-effort and less reliable than .xlsx
• Not suitable for public or multi-user hosting

---

License

MIT