mailmcp

mailmcp

All your mailboxes in ChatGPT and Claude. Passwords stay yours.

mailmcp is a self-hosted MCP server that gives ChatGPT, Claude and other MCP clients access to your e-mail over IMAP and SMTP: several mailboxes at once, any provider, attachments in both directions. This repository is the prebuilt distribution (minified bundles in dist/, no build step) under a commercial licence; it runs as a free tier without a key. The source code is not provided.

Ask *"What came in from accounting this week?"* and get one answer across Gmail, iCloud and the company mail server: the invoice as a download link, a reply already drafted.

When to use it

Use mailmcp when you have more than one mailbox, a provider without an official connector, or you need attachments. As of September 2026 the official Gmail and Outlook connectors in ChatGPT and Claude handle one mailbox each and cannot send attachments.

Quickstart

Requirements. Node 22 (or Vercel, or Docker), an HTTPS address (ChatGPT and Claude only connect over HTTPS), and an app password for each mailbox. Gmail: turn on 2-Step Verification first, otherwise Google hides the app-passwords page (organisation policies or Advanced Protection can hide it too). Outlook.com and Microsoft 365 need no password: the user signs in at Microsoft on the setup page (see "Outlook and Microsoft 365" below).

1. Set an invite code. A server that issues user tokens must say who may create one, otherwise anyone who knows the address can spend your quota. Pick MAILMCP_INVITE_CODE (at least 8 characters) and hand it to the people who may create a token; without it the server issues no tokens and the setup page shows a notice for you. Forgot the code? Read it in your Vercel or Docker environment, or set a new one and redeploy: tokens already issued keep working. A deliberately public server sets MAILMCP_OPEN_SIGNUP=1 instead.

1. Deploy. Click the Vercel button above; it asks for MAILMCP_KEY (32 random bytes as base64url, node -e "console.log(require('crypto').randomBytes(32).toString('base64url'))"), MAILMCP_LICENSE (your key, or empty for the free tier) and the invite code from step 1. Or run it yourself:

   docker build -t mailmcp . && docker run -d -p 8080:8080 \

-e MAILMCP_KEY=… -e MAILMCP_LICENSE=… -e MAILMCP_INVITE_CODE=… \ -e MAILMCP_PUBLIC_URL=https://mail.example.com mailmcp

without Docker: node dist/node.js with the same variables

1. Open `https:// /start` and follow it: on the setup page pick the provider, paste the e-mail and the app password, tick what the assistant may do (reading is on by default; drafts are a good second step; sending only with an allowlist of recipients). The page encrypts the password in your browser and hands you one token.

1. Connect. ChatGPT → Settings → Apps → Create → URL https:// /mcp; claude.ai → Settings → Connectors → Add custom connector. Sign in with the token. Then ask: *"List my mail accounts."*

Try it without deploying. The shared server at mailmcp.ai/setup runs this same code; create a token there and connect. The operator of any shared server can technically see your configuration while it serves your requests, which is why companies run their own.

Claude Desktop, no server. Download mailmcp.mcpb from the latest release, open it in Claude Desktop, paste the configuration from /setup → "Values for your own deployment".

Behind a reverse proxy set MAILMCP_PUBLIC_URL or MAILMCP_TRUST_PROXY=1. Company mail servers on private addresses need MAILMCP_ALLOW_PRIVATE_MAIL_HOSTS=1. Changing MAILMCP_KEY invalidates every token. All variables: .env.example.

Outlook and Microsoft 365

These mailboxes have no password: Microsoft rejects password sign-in on most accounts. The user picks the provider Outlook / Microsoft 365 on /setup and clicks Sign in with Microsoft. This needs your own Entra app registration (MAILMCP_MS_CLIENT_ID, steps below); without it the setup page offers no Microsoft sign-in. When your server's origin is a registered redirect URI (MAILMCP_MS_REDIRECT=1) the button opens a popup with the account picker; otherwise the page asks whether the user signs in with a personal account (Outlook.com, Hotmail) or a work or school account (Microsoft 365) and shows a short code to type at microsoft.com/link or login.microsoft.com/device respectively. Either way the sign-in sits behind your invite code (the device-code relay requires one even with MAILMCP_OPEN_SIGNUP=1), and your users see your app's name on the consent screen. No token reaches the vendor: your server runs the sign-in.

What to tell your users: at most three Outlook mailboxes per token; the consented Microsoft permissions follow the capabilities they tick (Mail.Read for read-only, otherwise Mail.ReadWrite and Mail.Send), so widening them later needs a new sign-in; a sign-in lasts about 90 days (the date is on /setup and in list_accounts as reauth_by, and clients that refresh through our OAuth have it rolled automatically); changing the mailbox password does not end it, revoking the app at Microsoft does, for every token that used that account. Tenants that leave consent to administrators need a one-off approval at https://login.microsoftonline.com/organizations/adminconsent?client_id= . Mail then flows over Microsoft Graph, so message ids are strings rather than numbers and labels are Outlook categories. Full guide: mailmcp.ai/docs.

Your own Microsoft app registration

Microsoft sign-in on your server needs an app registration of your own (the vendor's registration is used on mailmcp.ai only). Register it and use the popup flow, which works for personal and work accounts alike; new Microsoft 365 tenants block sign-in with a code (security defaults, AADSTS530035):

1. Microsoft Entra → App registrations → New registration; supported account types: Accounts in any organizational directory and personal Microsoft accounts.
2. Authentication → add the platform Mobile and desktop applications (not Web) with the redirect URI https:// /api/ms/callback. mailmcp is a public client with no secret; under the Web platform Microsoft demands one and the sign-in fails with AADSTS7000218.
3. Authentication → Allow public client flows: Yes.
4. API permissions → delegated Microsoft Graph Mail.Read, Mail.ReadWrite, Mail.Send, User.Read, offline_access.
5. Set MAILMCP_MS_CLIENT_ID= and MAILMCP_MS_REDIRECT=1, redeploy.

Tenants that allow user consent only for verified publishers additionally need publisher verification on your registration (Microsoft AI Cloud Partner Program), or an admin's consent for the whole tenant.

What the assistant can do

Every tool is gated by the permissions in the token, per mailbox:

| read (default) | list_accounts, list_folders, search_messages (Gmail syntax on Gmail), get_message, get_thread, get_attachment (one-hour download link), ChatGPT search/fetch, triage, awaiting_replies, digest