Originally published at postageformac.com. We make Postage.
An email MCP server is the bridge that lets an AI agent like Claude or Codex search, read and act on your mail. Before you connect one, check four things: where it runs, which accounts it covers, whether the agent can send without you, and whether you can see and undo what the agent changed.
The three kinds
- Hosted servers. A mail service runs the server and your agent connects over the internet with a sign-in. Usually tied to that service's accounts (often Gmail and Outlook).
- Scripts that drive another mail app. A small program you install with Node.js or Python that controls the mail app you already use through automation. You manage the install, updates and macOS permissions yourself.
- Built into a mail client. The mail app itself hosts the server, so the agent sees exactly what you see, and the app can show what the agent did. Postage works this way.
The checklist
| Question | Why it matters | Postage |
|---|---|---|
| Where does it run? | A server on the internet is reachable from the internet | 127.0.0.1:47913 only, no network mode |
| Which accounts? | Many servers cover one provider | Every IMAP account you add |
| Can the agent send on its own? | A prompt injection in one email could send mail as you | No. You press Send in a compose window |
| Is email treated as untrusted? | Email bodies are written by strangers | Bodies are marked as untrusted content; suspicious mail is flagged |
| Can you limit access? | An agent that only summarizes needs no write access | Read only, Organize and draft, or Full, per agent |
| Can you see and undo changes? | Agents make mistakes in batches | Every change listed, Undo for a week, one Undo per batch |
| One token per agent? | So you can cut off one agent without the others | Yes, in your Keychain, revocable one at a time |
| What does it cost? | Some servers come with a paid plan of the mail service | $39 once, no subscription |
Connecting any MCP client to Postage
Postage has one-click setup for Claude Code, Codex, Claude Desktop, Cursor, VS Code, Windsurf, Zed and Gemini CLI. Anything else that speaks MCP over Streamable HTTP with a bearer token can connect with these details (choose Other in Settings > Agents for a token):
Connection details:
URL: http://127.0.0.1:47913/mcp
Transport: Streamable HTTP
Header: Authorization: Bearer YOUR_POSTAGE_TOKEN
Per-client setup is on the Agents page.
Questions
What is MCP?
The Model Context Protocol, an open standard for connecting AI apps to tools and data. Claude, Codex, Cursor, VS Code and many others support it, so one server works with all of them.
Is Postage's MCP server reachable from my network?
No. It listens on 127.0.0.1 only (default port 47913). Other devices and the internet can't reach it, and it runs only while Postage is open.
Which macOS versions does Postage support?
macOS 14 Sonoma or later.
Postage is $39 once, for macOS 14 Sonoma or later: https://postageformac.com/pricing
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