# Atomic Mail (MCP server)

> Atomic Mail is an MCP server that adds messaging tools to AI assistants such as Claude Desktop, Claude Code and Cursor. Programmable email inbox for AI agents — JMAP, PoW auth, stdio MCP server. It has 266 GitHub stars, is released under the MIT license and runs locally with npx -y @atomicmail/mcp-modelcontextprotocol.

                           Accounts are free, with a 100 MB storage quota, custom domain included, and rate limits sized for agent workloads.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/Atomic-Mail/atomic-mail-agentic |
| GitHub stars | 266 |
| License | MIT |
| Language | TypeScript |
| Transport | stdio, streamable-http |
| Packages | npm: @atomicmail/mcp-modelcontextprotocol |
| Remote URL | https://mcp.atomicmail.ai/mcp |
| Needs API key | yes |
| Official | no |
| Works with | Claude Desktop, Claude Code, Cursor, VS Code, Claude.ai, ChatGPT |
| Category | Communication |
| Latest release | v0.3.31 (Sep 27, 2026) |
| Last commit | Sep 27, 2026 |
| MCP registry name | io.github.Atomic-Mail/mcp |

## Install

### Claude Desktop (claude_desktop_config.json)

```json
{
  "mcpServers": {
    "atomic-mail": {
      "command": "npx",
      "args": [
        "-y",
        "@atomicmail/mcp-modelcontextprotocol"
      ],
      "env": {
        "ATOMIC_MAIL_CREDENTIALS_DIR": "your-value",
        "ATOMIC_MAIL_API_KEY": "your-value",
        "ATOMIC_MAIL_AUTH_URL": "your-value"
      }
    }
  }
}
```

Settings > Developer > Edit Config. macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\. Restart Claude Desktop afterwards.

### Claude Code

```sh
claude mcp add --env ATOMIC_MAIL_CREDENTIALS_DIR=your-value --env ATOMIC_MAIL_API_KEY=your-value --env ATOMIC_MAIL_AUTH_URL=your-value --transport stdio atomic-mail -- npx -y @atomicmail/mcp-modelcontextprotocol
```

### Cursor (.cursor/mcp.json)

```json
{
  "mcpServers": {
    "atomic-mail": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@atomicmail/mcp-modelcontextprotocol"
      ],
      "env": {
        "ATOMIC_MAIL_CREDENTIALS_DIR": "your-value",
        "ATOMIC_MAIL_API_KEY": "your-value",
        "ATOMIC_MAIL_AUTH_URL": "your-value"
      }
    }
  }
}
```

Project file; use ~/.cursor/mcp.json to enable it in every project.

### VS Code (.vscode/mcp.json)

```json
{
  "inputs": [
    {
      "type": "promptString",
      "id": "atomic_mail_credentials_dir",
      "description": "ATOMIC_MAIL_CREDENTIALS_DIR",
      "password": true
    },
    {
      "type": "promptString",
      "id": "atomic_mail_api_key",
      "description": "ATOMIC_MAIL_API_KEY",
      "password": true
    },
    {
      "type": "promptString",
      "id": "atomic_mail_auth_url",
      "description": "ATOMIC_MAIL_AUTH_URL",
      "password": true
    }
  ],
  "servers": {
    "atomic-mail": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@atomicmail/mcp-modelcontextprotocol"
      ],
      "env": {
        "ATOMIC_MAIL_CREDENTIALS_DIR": "${input:atomic_mail_credentials_dir}",
        "ATOMIC_MAIL_API_KEY": "${input:atomic_mail_api_key}",
        "ATOMIC_MAIL_AUTH_URL": "${input:atomic_mail_auth_url}"
      }
    }
  }
}
```

### Claude Code (remote)

```sh
claude mcp add --transport http atomic-mail "https://mcp.atomicmail.ai/mcp"
```

The same server is also hosted as a remote MCP endpoint, so nothing runs on your machine.

Config formats checked against the official docs on 2026-10-07.

## Environment variables

- `ATOMIC_MAIL_CREDENTIALS_DIR` (secret): Override default credential directory (~/.atomicmail/)
- `ATOMIC_MAIL_API_KEY` (secret): Existing API key — skips PoW registration
- `ATOMIC_MAIL_AUTH_URL` (secret): Override auth service base URL
- `ATOMIC_MAIL_API_URL`: Override JMAP API base URL
- `ATOMIC_MAIL_INBOX_DOMAIN`: Default inbox domain when inboxId has no @ (default: atomicmail.ai)

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