mailosaur_messages_reply · Mailosaur MCP: Risk & Policy

WHAT IT DOES

What mailosaur_messages_reply does on Mailosaur MCP

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

WHY IT NEEDS A POLICY

Why mailosaur_messages_reply needs a policy

This tool sends a reply to an existing email message, which creates new outbound email data. It is a write/create action with moderate blast radius if misused (e.g., sending unintended replies), but it is reversible in the sense that it doesn't destroy existing data.

From the tool's definition Reply to an email message

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mailosaur_messages_reply Rate-limited

mailosaur_messages_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": {
    "mailosaur_messages_reply": {
      "limits": [
        {
          "counter": "mailosaur_messages_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 Mailosaur MCP, so you can run agents against it safely.

FAQ

Questions about mailosaur_messages_reply

What does the mailosaur_messages_reply tool do? +

Reply to an email message. It is categorised as a Write tool in the Mailosaur 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 mailosaur_messages_reply? +

Register the Mailosaur MCP server in PolicyLayer and add a rule for mailosaur_messages_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 Mailosaur MCP. Nothing to install.

What risk level is mailosaur_messages_reply? +

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

Can I rate-limit mailosaur_messages_reply? +

Yes. Add a rate_limit block to the mailosaur_messages_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 mailosaur_messages_reply completely? +

Set action: deny in the PolicyLayer policy for mailosaur_messages_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 mailosaur_messages_reply? +

mailosaur_messages_reply is provided by the Mailosaur MCP server (mrnewdelhi/mailosaur-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.