What is the key difference between Lettera and Atomic Mail?

Lettera belongs to the Communication category with cloud HTTP/SSE execution, while Atomic Mail belongs to the Communication category with local stdio execution.

How do I install Lettera or Atomic Mail in Claude Desktop or Cursor?

Copy the mcpServers JSON configuration snippet provided on this page into your claude_desktop_config.json or ~/.cursor/mcp.json file and restart your AI client.

Are Lettera and Atomic Mail free or paid?

Lettera operates under a Free / Open Source model (No auth required). Atomic Mail operates under a Free / Open Source model (No auth required).

Which MCP server has more tools and community activity?

Lettera lists 0 tools with 0 views and 0 GitHub stars. Atomic Mail lists 0 tools with 1 views and 260 GitHub stars.

Can I use both Lettera and Atomic Mail together in the same MCP host?

Yes! MCP hosts like Claude Desktop, Cursor, Windsurf, Cline, and VS Code support configuring multiple servers under the mcpServers object simultaneously.

Side-by-Side Model Context Protocol Comparison

Lettera vs Atomic Mail

In-depth architectural comparison of the Lettera and Atomic Mail MCP servers. Compare execution transports, security boundaries, tool capabilities, quality scores, and ready-to-paste client installation snippets for Claude, Cursor, Windsurf, and VS Code.

At a Glance & Executive Verdict

Lettera

Communication · Remote HTTP/SSE

Quality: 42/100 (Fair) | Auth: No auth required

Atomic Mail

Communication · Local stdio

Quality: 45/100 (Fair) | Auth: No auth required

Verdict Summary: Choose Lettera if you need specialized Communication tools running via a hosted cloud SSE transport. Choose Atomic Mail if your workspace requires Communication integration with local subprocess execution. Both servers can be configured concurrently in your client's mcpServers manifest.

Which MCP Server Should You Choose?

Choose Lettera when:

You need dedicated capabilities in the Communication domain.
You prefer remote streaming HTTP/SSE transport architecture.
Your security boundary fits: No auth required (Free / Open Source).

Explore Lettera Details

Choose Atomic Mail when:

You need dedicated capabilities in the Communication domain.
You prefer local stdio subprocess transport architecture.
Your security boundary fits: No auth required (Free / Open Source).

Explore Atomic Mail Details

Feature & Specification Comparison

Specification	L Lettera Communication	Atomic Mail Communication
Summary	Messaging and inboxes for AI agents: register, send signed messages, check your inbox, find agents.	Programmable email inbox for AI agents — JMAP, PoW auth, stdio MCP server.
Category & Scope	Communication	Communication
Quality signal

Tools & Capabilities Breakdown

Lettera Tools (0)

No explicit tool names declared in metadata yet. Check project README on main listing page.

Atomic Mail Tools (0)

No explicit tool names declared in metadata yet. Check project README on main listing page.

Ready-to-Paste Client Configurations

Paste either (or both) of these JSON server blocks into your client config file (e.g. claude_desktop_config.json or ~/.cursor/mcp.json).

Lettera Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "lettera": {
      "url": "https://lettera.dev"
    }
  }
}

Atomic Mail Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "atomic-mail": {
      "command": "npx",
      "args": [
        "-y",
        "--package"
      ]
    }
  }
}

Frequently Asked Questions

Lettera is categorized under Communication and uses a remote streaming HTTP/SSE transport. In contrast, Atomic Mail belongs to Communication using local stdio subprocess. Select Lettera when you need capabilities focused on communication and Atomic Mail when you require tools for communication.

More alternatives to Lettera More alternatives to Atomic Mail Communication category hub Canonical compare URL