reply_email · Email MCP: Risk & Policy

WHAT IT DOES

What reply_email does on Email

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

WHY IT NEEDS A POLICY

Why reply_email needs a policy

Replying to an email sends an outbound message on behalf of the user, which is a write/send operation. While it could be categorized as Execute (triggering external communication), the core action is composing and sending data. The blast radius is high because a misused reply could send sensitive, embarrassing, or malicious content to real recipients from the user's actual email account with no easy recall.

From the tool's definition 'reply_email' - replying to an email creates a new outbound message; description truncated but name clearly indicates sending a reply

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

reply_email Rate-limited

reply_email 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": {
    "reply_email": {
      "limits": [
        {
          "counter": "reply_email_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 Email, so you can run agents against it safely.

FAQ

Questions about reply_email

What does the reply_email tool do? +

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

How do I enforce a policy on reply_email? +

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

What risk level is reply_email? +

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

Can I rate-limit reply_email? +

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

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

reply_email is provided by the Email MCP server (kerodkibatu/email-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.