forward_message · Mail MCP: Risk & Policy

WHAT IT DOES

What forward_message does on Mail

AI agents use forward_message to create or update resources in Mail — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mail environment.

WHY IT NEEDS A POLICY

Why forward_message needs a policy

Forwarding a message is a Write operation—it creates new email content and sends it to recipients, modifying the email system state reversibly. It's not Destructive (no permanent deletion), Execute (no arbitrary code), or Financial (no money movement).

From the tool's definition Tool name 'forward_message' from email server (mail-mcp) with capability to forward messages. Server description confirms 'sending messages' and 'managing email workflows' are core functions.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

forward_message Rate-limited

forward_message stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "forward_message": {
      "limits": [
        {
          "counter": "forward_message_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Mail, so you can run agents against it safely.

FAQ

Questions about forward_message

What does the forward_message tool do? +

forward_message. It is categorised as a Write tool in the Mail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on forward_message? +

Register the Mail MCP server in PolicyLayer and add a rule for forward_message: 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 Mail. Nothing to install.

What risk level is forward_message? +

forward_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit forward_message? +

Yes. Add a rate_limit block to the forward_message 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 forward_message completely? +

Set action: deny in the PolicyLayer policy for forward_message. 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 forward_message? +

forward_message is provided by the Mail MCP server (kpihx/mail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.