mail_reply · Outpost MCP: Risk & Policy

WHAT IT DOES

What mail_reply does on Outpost

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

WHY IT NEEDS A POLICY

Why mail_reply needs a policy

Sending a reply to an email creates a new message and delivers it externally, which is a write/send operation. While it has external effects, it is not irreversible in the destructive sense nor financial. The blast radius is medium because an AI agent could send unintended replies to real recipients.

From the tool's definition Reply to an email in Outlook

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mail_reply Rate-limited

mail_reply 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": {
    "mail_reply": {
      "limits": [
        {
          "counter": "mail_reply_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 Outpost, so you can run agents against it safely.

FAQ

Questions about mail_reply

What does the mail_reply tool do? +

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

How do I enforce a policy on mail_reply? +

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

What risk level is mail_reply? +

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

Can I rate-limit mail_reply? +

Yes. Add a rate_limit block to the mail_reply 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_reply completely? +

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

mail_reply is provided by the Outpost MCP server (signalclaude/outpost). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.