Outlook Classic MCP

Claude / Codex  ──MCP──▶  outlook-classic-mcp.exe  ──COM──▶  Outlook (classic)  ──▶  your mailbox

Why

• No Azure app, no Graph API, no tokens. It talks to your running Outlook via COM and uses the session you are already signed in with. Nothing to register, no admin consent.

• Works where Microsoft Graph is blocked — e.g. by Conditional Access or token protection policies. If Outlook works on your PC, this works.

• Local only. Your mail never leaves your machine except to the AI client you use.

• Sends only if you allow it. Out of the box everything outgoing becomes a draft you review and send yourself — meeting invitations and replies to invitations included. Sending is an explicit opt-in (--allow-send), and even then only drafts go out.

• Audit log. Every change the assistant makes — drafts, sends, moves, deletes, calendar — is logged locally as one JSON line, without the message text.

• Files stay fenced in. Attachments can only be added from — and saved to — your user profile and %TEMP%, so a crafted email can't talk the assistant into attaching arbitrary files.

• One small EXE. No Python, no PowerShell, no runtime, no background service.

Related MCP server: mcp-outlook-desktop

Requirements

• Windows with classic Outlook (Outlook for Microsoft 365 / 2016 / 2019 / 2021 desktop, the Win32 app) set up with your mailbox. The new Outlook (“Outlook for Windows”, olk.exe) has no COM interface — see Using the new Outlook? below.

• An MCP client: Claude Desktop, Claude Code, Codex, Cursor, VS Code, …

• Run it as your normal user, not elevated (an admin process cannot attach to your Outlook).

Install

In PowerShell:

irm https://raw.githubusercontent.com/jli-software/outlook-classic-mcp/main/install.ps1 | iex

This downloads the latest release to %LOCALAPPDATA%\Programs\outlook-classic-mcp, checks its SHA-256 and registers it as server outlook in Claude Desktop, Claude Code and Codex. Restart your clients — done.

Claude Desktop only: download outlook-classic-mcp.mcpb from the latest release and open it — Claude Desktop installs it as an extension.

1. Download outlook-classic-mcp-windows-x64.exe from the latest release and save it as outlook-classic-mcp.exe wherever you like.

2. Register it:

   .\outlook-classic-mcp.exe install           # Claude Desktop, Claude Code, Codex
   .\outlook-classic-mcp.exe install --allow-send  # same, with sending enabled
   .\outlook-classic-mcp.exe install --print   # dry run: only show the config files
   .\outlook-classic-mcp.exe install codex     # only one target (desktop | code | codex)

   Existing configs are kept; a .outlook-classic-mcp.bak backup is written first.

Windows SmartScreen may warn about the unsigned EXE — “More info → Run anyway”.

Add a stdio server to your client's MCP config:

{
  "mcpServers": {
    "outlook": {
      "command": "C:\\Users\\you\\AppData\\Local\\Programs\\outlook-classic-mcp\\outlook-classic-mcp.exe",
      "args": ["serve"]
    }
  }
}

What you can ask

“Summarize my unread mail from today.” “Find the invoice from Contoso in all folders and save the PDF.” “Draft a reply to Anna's last mail: Thursday works, 10am.” “Move all newsletters from this week to Archive and mark them read.” “What's Anna Smith's email and department? Draft her an invite for Friday.” “What's on my calendar this week? When are Anna and Beat both free on Tuesday?” “Move my 2pm dentist appointment to Thursday and set a reminder 1 hour before.”

Tools

Without --allow-send there is no send tool at all. In the calendar this means: a new meeting stays unsent until you click Send in Outlook, a response to an invitation lands in Drafts, and changing or deleting a meeting does not notify anyone — deleting a meeting you organize whose invitations were already sent is refused, so attendees aren't left with a ghost meeting (cancel it in Outlook instead).

Times go in and out as ISO 8601 in your local time (2026-10-29T14:00); a date alone (2026-10-29) makes an all-day event. An offset (+01:00, Z) is converted to local time.

Email addresses always come back as SMTP addresses (anna.smith@contoso.com), also for Exchange senders and directory entries — never as /O=…/CN=….

Sending

Sending is off by default. To allow it, register the server with install --allow-send (or add "--allow-send" after "serve" in your client's args) and restart the client. Running install without the flag turns it off again.

With sending on, the assistant still writes a draft first; mail_send_draft then sends it, and the tool tells the assistant to do so only after you have confirmed that exact draft. It refuses anything that is not an email or a meeting response in your Drafts folder, and it sends nothing if a recipient can't be resolved. Meetings are never sent by the server — invitations, updates and cancellations stay with you in Outlook.

Sent mail first goes to the Outbox; classic Outlook delivers it on its next sync (with Outlook running, within seconds).

Outlook security prompt: Outlook may show a warning that “a program is trying to send an email on your behalf” (the Object Model Guard). On PCs with an up-to-date, recognized antivirus this normally doesn't appear; where it does, sending waits for your click and times out after 90 s. Admins can control it with the Outlook policy Programmatic Access Security.

Audit log

Every action that changes something is appended as one JSON line to %LOCALAPPDATA%\outlook-classic-mcp\audit.log:

{"time":"2026-10-29T10:32:33+01:00","tool":"mail_send_draft","id":"00000000…","ok":true,"subject":"Offer","to":["anna.smith@contoso.com"]}

It records time, tool, IDs, recipients, subject and the result — never the message text. The file rotates at 5 MB (audit.log.1). Set OUTLOOK_MCP_AUDIT_LOG in the server's environment to another path, or to off. outlook_whoami shows where it is written.

Attachment folders

mail_reply (attachments) and mail_save_attachment (dir) only accept paths under your user profile (%USERPROFILE%) or %TEMP%; anything else is refused. To lift this, set OUTLOOK_MCP_ALLOW_ANY_PATH=1 in the server's environment, e.g.

"outlook": { "command": "…\\outlook-classic-mcp.exe", "args": ["serve"],
             "env": { "OUTLOOK_MCP_ALLOW_ANY_PATH": "1" } }

Using the new Outlook?

You can keep working in the new Outlook. The classic Outlook only has to be installed and should run now and then, because this server reads its local cache:

• Best: start classic Outlook minimized with Windows. You won't notice it, and the cache stays fresh. Turn off its desktop notifications so you don't get every mail twice (File → Options → Mail → Display a Desktop Alert).

  $s  = New-Object -ComObject WScript.Shell
  $sc = $s.CreateShortcut("$env:APPDATA\Microsoft\Windows\Start Menu\Programs\Startup\Outlook (classic).lnk")
  $sc.TargetPath  = (Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\OUTLOOK.EXE').'(default)'
  $sc.WindowStyle = 7   # minimized
  $sc.Save()

• On demand: ask the assistant to run mail_sync first.

If classic Outlook is closed, the server starts it invisibly and releases it again after 5 minutes without a call.

Troubleshooting

Build from source

git clone https://github.com/jli-software/outlook-classic-mcp
cd outlook-classic-mcp
go build -o outlook-classic-mcp.exe .
go test .

Pure Go (no CGO), using go-ole for COM and mcp-go for MCP.

Disclaimer

This is an independent open-source project. It is not affiliated with, endorsed by or sponsored by Microsoft. “Microsoft” and “Outlook” are trademarks of the Microsoft group of companies.

License

MIT