Compatibility
One mailbox. Any MCP client.
MCP is an open protocol rather than one company's feature, and this is an ordinary MCP server. Connect a mailbox once and reach it from whichever assistant, editor or agent you actually work in.
- Protocol Model Context Protocol
- Transport Remote, over HTTPS
- Extra cost None, per client
Clients
Clients that speak MCP
A selection of the better known ones, described by what they are rather than by a tick in a box. If yours is not here it is not a statement about your client; the list is illustrative and the requirement below is the thing that actually decides it.
- Claude Assistant On the web, in the desktop app and in Claude Code. The one most people arrive here already using.
- ChatGPT Assistant Through its connector settings, where your plan and mode allow custom MCP connectors.
- Cursor Code editor Mail tools alongside your codebase, which is more useful than it sounds when the bug arrived by email.
- VS Code Code editor Through agent mode, which reads MCP servers from your workspace or user configuration.
- Zed Code editor As a context server, configured per project or globally.
- Windsurf Code editor Added to its MCP configuration like any other server.
- Cline Coding agent An open-source agent that has supported MCP servers since early on.
- Goose Open agent Block's open-source agent, which treats MCP servers as extensions.
- LibreChat Self-hosted For teams running their own chat interface against whichever model they prefer.
- Copilot Studio Agent platform Microsoft's agent builder, which can consume MCP servers as tools.
- Your own agent MCP SDK The SDKs speak the protocol directly. If you have written an agent, it can hold a mailbox.
What it needs
The one requirement
Your client has to support remote MCP servers, not only local ones.
The distinction matters because MCP arrived with local servers first. Early clients were built to launch a server as a process on your own machine and talk to it over standard input and output, which is a fine design for a tool that reads your filesystem and a useless one for a mailbox you want to reach from your phone. Mailbox MCP is hosted, so your client needs to be able to talk to a server it did not start itself.
Most clients now can. If yours offers to add a connector by URL, it can. If it only offers to run a command, see the next section.
The workaround
If your client only does local servers
A small proxy bridges the two. It runs on your machine, presents itself to your client as an ordinary local MCP server, and forwards everything to ours over HTTPS.
npx mcp-remote https://your-server-url
The guide to the two transports covers what that proxy is actually doing, and quotes the current specification, which most write-ups of this get wrong.
Your client sees a local server and behaves normally. The trade is that the connection is only live while that machine is, which is precisely the thing a remote server otherwise saves you from, so treat it as a way in rather than as the destination.
Open protocol
Why this matters
Mail integrations have historically been bought per application. A tool for Outlook, a different tool for your CRM, a third thing bolted onto whatever your team uses to chat. Each one holds its own copy of your credentials and each one has to be revoked separately when you stop using it. A dedicated AI email assistant is built the same way, with its own interface and its own copy of your mailbox credentials; see the two approaches to putting AI on your inbox for when that trade suits you better than connecting the AI you already pay for.
An open protocol changes the shape of that. The connection belongs to your account rather than to an application, so you authorise a mailbox once and every client you use reaches the same one, with the same permissions, revocable in one place. Change editors next year and the mailbox comes with you.
It also means you are not betting your mail setup on our guess about which assistant wins. That is worth something to you and it is worth being honest about from our side: we would rather be the mailbox layer for whatever you end up using than the reason you cannot move.
Limits
What cannot connect
Stated as plainly as the rest, because a compatibility page that only lists successes is an advert.
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No MCP client at all
An assistant with no MCP client at all, and which products those are changes month to month.
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Blocked by your IT
A managed or corporate deployment where your administrator has blocked third-party connectors.
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No way to add a server
A client that supports MCP but offers no way to add a server you choose yourself.
Check your client, not our list
Support moves quickly. Look for connectors, MCP servers, tools or extensions in your client's own settings, and trust that over any table on a supplier's website, this one included.
Questions
Questions about clients and compatibility
Does Mailbox MCP only work with Claude?
No. It is an ordinary MCP server reached over HTTPS with a bearer token, and nothing in it is specific to one assistant. Claude is what most people arrive already using, which is why the rest of the site names it, but the same URL works in Cursor, VS Code, Zed, Cline, Goose, LibreChat, ChatGPT and any agent written against an MCP SDK.
Is there a different price for using it with something other than Claude?
No. There is one price and it is per mailbox, not per client or per seat. You can connect the same mailbox from your editor and your phone and it is still one mailbox.
Can I use one mailbox from more than one AI client at once?
Yes. The connection belongs to your account rather than to a device or an application, so the same mailbox can be reached from Claude on your phone and from your editor on your desktop. Calls from all of them count towards the same daily limit on a free mailbox.
My client only supports local MCP servers. Can I still use this?
Yes, through a small local proxy such as mcp-remote, which runs on your machine, presents itself to your client as a local server, and forwards to ours. Once it is running the connection behaves like any other. It does mean the connection is only live while that machine is, which is the thing a remote server otherwise saves you from.
Which mailboxes work, and do they all get the calendar tools?
Every mailbox works: Microsoft 365 with one Microsoft sign-in, Gmail with an app password, and any other host with its IMAP and SMTP settings. All of them get the same email tools. The calendar is the one thing that differs, because connecting a mailbox does not connect a diary. A Microsoft 365 mailbox gets the calendar tools when its owner approves calendar access on the same sign-in. Every other mailbox has two routes to a diary and can use either: a Google sign-in for Google Calendar, or the address of a CalDAV calendar server, which Fastmail, iCloud, Nextcloud and most mail hosts run. A mailbox with none of them is handed no calendar tools at all rather than tools that would refuse, because one certain to fail still spends a call against your daily allowance to say so.
Can I connect Google Calendar?
Yes, on any mailbox, whoever hosts the mail. It is its own sign-in rather than part of the mail connection, and that is not a workaround: an app password is a mail credential that opens IMAP and SMTP and nothing else, and Google refuses one on its own CalDAV endpoint too, so there was never an address to paste. You press Connect Google Calendar in the control panel, choose an account, and Google shows you what is being asked for before you approve it. The account does not have to be the one the mailbox is on, which is useful when the work diary and the work mail are not the same Google account. The permission covers the diary only, never the mail, and you can withdraw it from your Google account at any time.
How do I know whether my AI client supports MCP?
Look for connectors, MCP servers, tools or extensions in its settings. We deliberately do not publish a compatibility matrix: support changes month to month across a dozen products and a table of ticks on our website would be out of date before it was useful. Your client's own documentation is the answer that stays current.
Connect a mailbox once.
Then reach it from wherever you actually work. 5 calls a day free, on any mailbox, with no card.