Mailbox MCP
Connect a mailbox
All documentation
Connect a mailbox Client not listed? Ask us
On this page

Set-up documentation

Connect your mailbox to Claude.ai

Add your mailbox to Claude on the web as a custom connector. One URL, no client ID, no client secret. The advanced OAuth boxes stay empty and that is the point.

Time About 2 minutes
Where Settings, then Connectors, then Add custom connector
It needs URL only, then sign in

Before you start

You need a mailbox already connected in the control panel. Claude cannot reach a mailbox we do not hold, and the panel is where the mail server credential is checked and kept. That takes about two minutes for Microsoft 365, a little longer for Gmail because Google wants an app password.

You do not need anything installed. Claude.ai talks to this server over HTTPS from Anthropic's own infrastructure, so there is no bridge program, no npx command and nothing running on your machine. That is the difference between a remote MCP server and a local one, and it is covered properly in remote and local MCP servers.

Add the connector

  1. Open Settings, then Connectors

    From your account menu in Claude.ai. The Connectors screen lists anything already attached, which on a new account is usually Anthropic's own set.

  2. Choose Add custom connector

    Name it after the mailbox, not after us. Claude lists connectors by that name for as long as it exists, and if you connect a second mailbox later the two entries are otherwise identical.

  3. Paste the connector URL

    Connector URL The same for every account 
    https://mcp.mailbox-mcp.com/db/mcp/YOUR-MAILBOX-KEY

    Then leave the advanced OAuth boxes alone. There is no client ID to find and no secret to paste, and the next section explains why.

  4. Press Connect and sign in

    Claude sends you to the control panel, you sign in, and it asks which of your mailboxes this connector should open. Choose one and you are returned to Claude with the tools attached.

Two mailboxes, one URL

The address is the same whichever mailbox you are connecting, because the mailbox is settled during the sign-in rather than by the URL. To add a second, repeat all four steps under a different name and pick the other mailbox when it asks.

Why the OAuth boxes stay empty

Claude's dialog has an advanced section with a client ID and a client secret in it, and most set-up guides for a remote MCP server tell you to go and fetch both. Leaving them empty here is correct rather than merely acceptable.

Those fields exist for a server that cannot register a client on its own, where somebody has to create an application by hand and copy the credentials across. This server publishes an authorisation server document that says it supports dynamic client registration, so Claude reads it, introduces itself, and is issued what it needs on the spot. Filling the boxes in does not make anything more secure. It gives the connection one more thing to get wrong, and puts a credential in your clipboard that never needed to be there.

Check that it worked

A connector that is set up correctly says nothing at all, so the way to check it is to use it. Start a new conversation and ask for something you can verify against your own mailbox at a glance.

Try this first

Summarise my five most recent unread emails, oldest first, and tell me which ones actually need me.

If the messages it names are the messages you expect, the connector works. Nothing is marked read by asking: reading through this server never sets the seen flag, so your own unread markers survive the test.

The control panel is the second check and the more definitive one. Open the mailbox and its connector card records when the connector was first used, so if that line has filled in, a call really did arrive here.

If something goes wrong

Three things account for nearly all of it, and none of them produce a useful error message on their own.

  • Symptom

    Claude says it has no email tools

    Check the connector is enabled for the conversation you are in. Connectors are added to the account and then chosen per conversation, so a connector that exists is not necessarily a connector this chat can reach.

  • Symptom

    The sign-in loops or ends on an error

    Almost always something pasted into the advanced OAuth fields. Remove the connector, add it again, and this time do not touch them.

  • Symptom

    Tools appear but every call fails

    The mailbox credential we hold has stopped working, which usually means the mailbox password changed or an app password was revoked. The panel says so on the mailbox card; update it there and nothing in Claude needs touching, because the connector URL has not changed.

No account yet? The free tier is 5 MCP calls a day on any mailbox, with no card, which is enough to get to the end of this page and see your own mail in Claude.

Connect a mailbox Sign in

Where to go next

The desktop app takes the same connector through the same screen, so if you use both, this is already done in both. Claude Code is one command instead.

The use cases are worth a look once it is working, and the tool reference lists everything Claude can now reach and marks which of those tools are read-only.

Read 30 August 2026 Verified against a live connector on that day. If it has changed since, tell us and we will read it again.

By Mark McNeece, Founder Published Last reviewed Editorial standards