reply_to_email · Microsoft MCP: Risk & Policy

WHAT IT DOES

What reply_to_email does on Microsoft MCP

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

WHY IT NEEDS A POLICY

Why reply_to_email needs a policy

Sending a reply creates a new email message directed at the original sender. This is a Write operation — it creates new data (an outbound email) but is reversible in the sense that it doesn't delete anything. However, it does trigger an external communication, which could have social or business consequences if misused.

From the tool's definition Reply to an email (sender only)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

reply_to_email Rate-limited

reply_to_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_to_email": {
      "limits": [
        {
          "counter": "reply_to_email_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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

FAQ

Questions about reply_to_email

What does the reply_to_email tool do? +

Reply to an email (sender only). It is categorised as a Write tool in the Microsoft MCP 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_to_email? +

Register the Microsoft MCP server in PolicyLayer and add a rule for reply_to_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 Microsoft MCP. Nothing to install.

What risk level is reply_to_email? +

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

Can I rate-limit reply_to_email? +

Yes. Add a rate_limit block to the reply_to_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_to_email completely? +

Set action: deny in the PolicyLayer policy for reply_to_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_to_email? +

reply_to_email is provided by the Microsoft MCP server (purva-kashyap/microsoft-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.