mail__list_messages

THE RISK

Low Risk

Why mail__list_messages needs a policy

This tool retrieves and queries email data without creating, modifying, deleting, or executing any operations. It is purely informational, consistent with Read category tools like 'list' and 'get'.

From the tool's definition Tool name contains 'list' and description states 'List recent emails from Proton Mail inbox' — a retrieval operation with no side effects.

Documented attack patterns abuse exactly the kind of access mail__list_messages gives an agent:

POLICY

How to control mail__list_messages

PolicyLayer is an MCP gateway — it sits between your AI agents and Proton-MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for mail__list_messages:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "mail__list_messages": {}
  }
}

mail__list_messages is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Proton-MCP — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about mail__list_messages

What does the mail__list_messages tool do? +

List recent emails from Proton Mail inbox. It is categorised as a Read tool in the Proton-MCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on mail__list_messages? +

Register the Proton- MCP server in PolicyLayer and add a rule for mail__list_messages: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Proton-MCP. Nothing to install.

What risk level is mail__list_messages? +

mail__list_messages is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit mail__list_messages? +

Yes. Add a rate_limit block to the mail__list_messages rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block mail__list_messages completely? +

Set action: deny in the PolicyLayer policy for mail__list_messages. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides mail__list_messages? +

mail__list_messages is provided by the Proton- MCP server (jorgenclaw/proton-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Proton-MCP tool call.

Start from Proton-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →