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Connect your mailbox to Cline

Cline spells the transport streamableHttp in camel case, alone among every client. OAuth is not in its documentation, so this one takes an access token.

By Mark McNeece, Founder Published Editorially reviewed by Mark McNeece on Editorial standards

Time About 3 minutes
Where MCP Servers icon, Remote Servers tab
It needs URL and an access token
Top-level key mcpServers
URL key url

Cline in 3 steps

  1. Create an access token

    In the control panel, create an access token for the mailbox you want Cline to reach. Cline does not document OAuth, so this is the working route.

  2. Add the server

    Under mcpServers, with type streamableHttp in camel case, a url of https://mcp.mailbox-mcp.com/db/mcp/YOUR-MAILBOX-KEY, and the token in an Authorization header.

  3. Check the tools appear

    Open the MCP Servers panel in Cline. The mail tools should be listed under the name you gave it.

This one takes an access token

Most clients in this section need nothing but a URL, because they sign you in. Cline is one of the ones that does not, and the reason is worth stating precisely rather than as a verdict: OAuth is not mentioned anywhere in Cline's own MCP documentation. 3 of its pages were read on 30 August 2026 and all 3 describe API keys, tokens and custom headers only.

That is a gap in the documentation rather than a documented refusal, so it is possible Cline handles a sign-in and simply has not written it down. The token route is what we can tell you works: create one in the control panel for the mailbox you want Cline to reach.

The token carries the mailbox's limit as its permission level, set on the same Connector tab: Send and delete with the calendar unless you lower it. If you do, Cline is held to whatever you lowered it to.

A token is a credential, so treat it like one

It opens one mailbox until you revoke it. Do not commit the file it lives in, do not paste it into a chat window, and revoke it in the control panel the moment you stop using it. Every client that signs in instead is one fewer of these in existence, which is the whole argument for the OAuth route where a client offers it.

The configuration

~/.cline/mcp.json Substitute your own token 
{
  "mcpServers": {
    "work-mail": {
      "type": "streamableHttp",
      "url": "https://mcp.mailbox-mcp.com/db/mcp/YOUR-MAILBOX-KEY",
      "headers": {
        "Authorization": "Bearer YOUR-ACCESS-TOKEN"
      },
      "disabled": false,
      "autoApprove": []
    }
  }
}

streamableHttp is camel case and Cline is alone in spelling it that way. Its documentation says to set this explicitly for the recommended transport, and to use "type": "sse" only for legacy SSE servers, which this is not.

autoApprove is worth a thought rather than a copy. An empty list means Cline asks before every call, which on a mailbox is the right default. If you do put tool names in it, put read tools there and nothing else: an auto-approved send_email is an agent that can send mail in your name without asking, and every auto-approved read still counts against your daily call limit.

Or add it through the panel

The same thing without editing a file: the MCP Servers icon, then the Remote Servers tab. It asks for a server name, a server URL, and a transport type, where the choices are Streamable HTTP (recommended) and SSE (Legacy). Pick the first. Then Add Server.

Which file

~/.cline/mcp.json is the only path in Cline's own documentation, and it is the CLI's. The VS Code extension keeps its settings somewhere under the editor's global storage, and that path is not vendor-documented anywhere we could find, so it is in the unconfirmed list at the foot of this page rather than printed here as though it were certain. If you use the extension, the panel route above avoids the question entirely.

Check that it worked

Try this first

Read my 3 most recent unread emails and tell me if any of them are about something in this codebase.

Nothing is marked read by asking. A 401 rather than a result means the token, not the URL: check you pasted the whole of it and that it has not been revoked.

The free tier is 5 MCP calls a day on any mailbox, with no card. Enough to try Cline against your own mail before deciding.

Connect a mailbox Sign in

Where to go next

If you also use VS Code's own agent mode, that one does sign you in and needs no token at all, which is the better arrangement where you have the choice. The key table shows which clients are which.

What we could not confirm
  • The IDE extension's settings path. Only the CLI path is in vendor documentation; the cline_mcp_settings.json location under globalStorage comes from third parties.
  • Whether Cline supports OAuth at all. It is not mentioned on any of 3 vendor pages read, which is why this page uses a token.

Read 30 August 2026 Every value on this page came off Cline documentation: MCP overview on that day. If it has changed since, tell us and we will read it again.