SMTP

io.github.ni-c/smtp-mcp · v0.2.0

MCP server that sends mail over SMTP, gated behind an allowlist and a human confirmation

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Connect Runs on your machine

Terminal

claude mcp add smtp-mcp -e SMTP_HOST=<SMTP_HOST> -e SMTP_PORT=<SMTP_PORT> -e SMTP_TLS=<SMTP_TLS> -e SMTP_USER=<SMTP_USER> -e SMTP_PASSWORD=<SMTP_PASSWORD> -e SMTP_FROM=<SMTP_FROM> -e SMTP_REPLY_TO=<SMTP_REPLY_TO> -e SMTP_ALLOW_SEND=<SMTP_ALLOW_SEND> -e SMTP_ALLOWED_RECIPIENTS=<SMTP_ALLOWED_RECIPIENTS> -e SMTP_MAX_RECIPIENTS=<SMTP_MAX_RECIPIENTS> -e SMTP_MAX_SENDS_PER_HOUR=<SMTP_MAX_SENDS_PER_HOUR> -e SMTP_MAX_MESSAGE_BYTES=<SMTP_MAX_MESSAGE_BYTES> -e SMTP_MAX_ATTACHMENT_BYTES=<SMTP_MAX_ATTACHMENT_BYTES> -e SMTP_ATTACHMENT_DIR=<SMTP_ATTACHMENT_DIR> -e SMTP_ATTACHMENT_TYPES=<SMTP_ATTACHMENT_TYPES> -e SMTP_SIGNATURE=<SMTP_SIGNATURE> -e SMTP_AUDIT_LOG=<SMTP_AUDIT_LOG> -e SMTP_ALLOW_TOOLS=<SMTP_ALLOW_TOOLS> -e SMTP_DENY_TOOLS=<SMTP_DENY_TOOLS> -e SMTP_INSECURE_TLS=<SMTP_INSECURE_TLS> -- npx -y @ni-c/[email protected]

claude_desktop_config.json

{
  "mcpServers": {
    "smtp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@ni-c/[email protected]"
      ],
      "env": {
        "SMTP_HOST": "<SMTP_HOST>",
        "SMTP_PORT": "<SMTP_PORT>",
        "SMTP_TLS": "<SMTP_TLS>",
        "SMTP_USER": "<SMTP_USER>",
        "SMTP_PASSWORD": "<SMTP_PASSWORD>",
        "SMTP_FROM": "<SMTP_FROM>",
        "SMTP_REPLY_TO": "<SMTP_REPLY_TO>",
        "SMTP_ALLOW_SEND": "<SMTP_ALLOW_SEND>",
        "SMTP_ALLOWED_RECIPIENTS": "<SMTP_ALLOWED_RECIPIENTS>",
        "SMTP_MAX_RECIPIENTS": "<SMTP_MAX_RECIPIENTS>",
        "SMTP_MAX_SENDS_PER_HOUR": "<SMTP_MAX_SENDS_PER_HOUR>",
        "SMTP_MAX_MESSAGE_BYTES": "<SMTP_MAX_MESSAGE_BYTES>",
        "SMTP_MAX_ATTACHMENT_BYTES": "<SMTP_MAX_ATTACHMENT_BYTES>",
        "SMTP_ATTACHMENT_DIR": "<SMTP_ATTACHMENT_DIR>",
        "SMTP_ATTACHMENT_TYPES": "<SMTP_ATTACHMENT_TYPES>",
        "SMTP_SIGNATURE": "<SMTP_SIGNATURE>",
        "SMTP_AUDIT_LOG": "<SMTP_AUDIT_LOG>",
        "SMTP_ALLOW_TOOLS": "<SMTP_ALLOW_TOOLS>",
        "SMTP_DENY_TOOLS": "<SMTP_DENY_TOOLS>",
        "SMTP_INSECURE_TLS": "<SMTP_INSECURE_TLS>"
      }
    }
  }
}

~/.cursor/mcp.json

{
  "mcpServers": {
    "smtp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@ni-c/[email protected]"
      ],
      "env": {
        "SMTP_HOST": "<SMTP_HOST>",
        "SMTP_PORT": "<SMTP_PORT>",
        "SMTP_TLS": "<SMTP_TLS>",
        "SMTP_USER": "<SMTP_USER>",
        "SMTP_PASSWORD": "<SMTP_PASSWORD>",
        "SMTP_FROM": "<SMTP_FROM>",
        "SMTP_REPLY_TO": "<SMTP_REPLY_TO>",
        "SMTP_ALLOW_SEND": "<SMTP_ALLOW_SEND>",
        "SMTP_ALLOWED_RECIPIENTS": "<SMTP_ALLOWED_RECIPIENTS>",
        "SMTP_MAX_RECIPIENTS": "<SMTP_MAX_RECIPIENTS>",
        "SMTP_MAX_SENDS_PER_HOUR": "<SMTP_MAX_SENDS_PER_HOUR>",
        "SMTP_MAX_MESSAGE_BYTES": "<SMTP_MAX_MESSAGE_BYTES>",
        "SMTP_MAX_ATTACHMENT_BYTES": "<SMTP_MAX_ATTACHMENT_BYTES>",
        "SMTP_ATTACHMENT_DIR": "<SMTP_ATTACHMENT_DIR>",
        "SMTP_ATTACHMENT_TYPES": "<SMTP_ATTACHMENT_TYPES>",
        "SMTP_SIGNATURE": "<SMTP_SIGNATURE>",
        "SMTP_AUDIT_LOG": "<SMTP_AUDIT_LOG>",
        "SMTP_ALLOW_TOOLS": "<SMTP_ALLOW_TOOLS>",
        "SMTP_DENY_TOOLS": "<SMTP_DENY_TOOLS>",
        "SMTP_INSECURE_TLS": "<SMTP_INSECURE_TLS>"
      }
    }
  }
}

.vscode/mcp.json

{
  "servers": {
    "smtp-mcp": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@ni-c/[email protected]"
      ],
      "env": {
        "SMTP_HOST": "<SMTP_HOST>",
        "SMTP_PORT": "<SMTP_PORT>",
        "SMTP_TLS": "<SMTP_TLS>",
        "SMTP_USER": "<SMTP_USER>",
        "SMTP_PASSWORD": "<SMTP_PASSWORD>",
        "SMTP_FROM": "<SMTP_FROM>",
        "SMTP_REPLY_TO": "<SMTP_REPLY_TO>",
        "SMTP_ALLOW_SEND": "<SMTP_ALLOW_SEND>",
        "SMTP_ALLOWED_RECIPIENTS": "<SMTP_ALLOWED_RECIPIENTS>",
        "SMTP_MAX_RECIPIENTS": "<SMTP_MAX_RECIPIENTS>",
        "SMTP_MAX_SENDS_PER_HOUR": "<SMTP_MAX_SENDS_PER_HOUR>",
        "SMTP_MAX_MESSAGE_BYTES": "<SMTP_MAX_MESSAGE_BYTES>",
        "SMTP_MAX_ATTACHMENT_BYTES": "<SMTP_MAX_ATTACHMENT_BYTES>",
        "SMTP_ATTACHMENT_DIR": "<SMTP_ATTACHMENT_DIR>",
        "SMTP_ATTACHMENT_TYPES": "<SMTP_ATTACHMENT_TYPES>",
        "SMTP_SIGNATURE": "<SMTP_SIGNATURE>",
        "SMTP_AUDIT_LOG": "<SMTP_AUDIT_LOG>",
        "SMTP_ALLOW_TOOLS": "<SMTP_ALLOW_TOOLS>",
        "SMTP_DENY_TOOLS": "<SMTP_DENY_TOOLS>",
        "SMTP_INSECURE_TLS": "<SMTP_INSECURE_TLS>"
      }
    }
  }
}

Replace the values in angle brackets with your own. Keys stay on your machine; we never see them.

Tools

This server runs locally, so its tools are listed by your MCP client once it starts.

Environment variables

Name	Description
`SMTP_HOST` Required	Hostname of the SMTP server, e.g. smtp.example.net.
`SMTP_PORT` Optional	Port. Defaults to 587 for starttls, 465 for implicit, 25 for none.
`SMTP_TLS` Optional	starttls (default), implicit or none. STARTTLS is required, never opportunistic.
`SMTP_USER` Required	Username for SMTP authentication.
`SMTP_PASSWORD` Required, secret	Password or app-specific password for SMTP authentication.
`SMTP_FROM` Required	The only sender this server will use, e.g. "Name <[email protected]>". There is no from parameter.
`SMTP_REPLY_TO` Optional	Reply-To header on every message, e.g. "Team <[email protected]>". Unset means no Reply-To header and replies go to SMTP_FROM. There is no reply_to parameter.
`SMTP_ALLOW_SEND` Optional	Set to "true" to register the sending tools. Defaults to false: the server cannot send until it is set.
`SMTP_ALLOWED_RECIPIENTS` Optional	Comma-separated addresses and @domains this server may write to. Required with SMTP_ALLOW_SEND=true; "*" allows any.
`SMTP_MAX_RECIPIENTS` Optional	Maximum distinct recipients across To, Cc and Bcc in one message. Default 10.
`SMTP_MAX_SENDS_PER_HOUR` Optional	Sliding hourly cap on messages sent. Default 20.
`SMTP_MAX_MESSAGE_BYTES` Optional	Maximum size of the composed message. Default 10485760.
`SMTP_MAX_ATTACHMENT_BYTES` Optional	Maximum size of a single attachment. Default 5242880.
`SMTP_ATTACHMENT_DIR` Optional	Directory attachments are read from. Unset means attachments are unavailable.
`SMTP_ATTACHMENT_TYPES` Optional	Comma-separated content types that may be attached. Defaults to a document and image allowlist.
`SMTP_SIGNATURE` Optional	Text appended below the standard signature delimiter of every message.
`SMTP_AUDIT_LOG` Optional	File the audit lines are appended to, in addition to stderr.
`SMTP_ALLOW_TOOLS` Optional	Comma-separated tool names, a prefix with one trailing *, or "essential" for the curated preset.
`SMTP_DENY_TOOLS` Optional	Comma-separated tool names or prefixes to remove, applied after SMTP_ALLOW_TOOLS.
`SMTP_INSECURE_TLS` Optional	Set to "true" to accept self-signed certificates. Prefer a proper internal CA.

Details

Package	`@ni-c/[email protected]` (NPM, stdio)
Package	`ghcr.io/ni-c/smtp-mcp:0.2.0` (OCI, stdio)
First published	7 Sep 2026
Last updated	7 Sep 2026
Registry name	`io.github.ni-c/smtp-mcp`

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Live status

Local install

Installed and run on your own machine, so there is no public endpoint to check.

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