zerosmtp for Claude Desktop

io.github.msgwing/zerosmtp

A free SMTP relay that still takes a username and password, for devices that cannot do OAuth 2.0.

client:Claude Desktop transport:stdio runtime:npm

Install zerosmtp in Claude Desktop

~/Library/Application Support/Claude/claude_desktop_config.json · windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "zerosmtp": {
      "command": "npx",
      "args": [
        "-y",
        "zerosmtp-mcp"
      ]
    }
  }
}

Settings → Developer → Edit Config opens this file. Restart the app after saving. Claude Desktop docs