configure_fastmail · FastMail MCP Server MCP: Risk & Policy

WHAT IT DOES

What configure_fastmail does on FastMail MCP Server

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

WHY IT NEEDS A POLICY

Why configure_fastmail needs a policy

This tool creates or modifies API credential configuration, which is a write operation. However, misconfiguration or injection of malicious credentials could compromise email account security and potentially expose sensitive data to unauthorized parties.

From the tool's definition Tool name is 'configure_fastmail' and description states 'Configure FastMail API credentials'. Configuring credentials modifies authentication settings in a reversible way.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

configure_fastmail Rate-limited

configure_fastmail 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": {
    "configure_fastmail": {
      "limits": [
        {
          "counter": "configure_fastmail_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 FastMail MCP Server, so you can run agents against it safely.

FAQ

Questions about configure_fastmail

What does the configure_fastmail tool do? +

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

How do I enforce a policy on configure_fastmail? +

Register the FastMail MCP Server MCP server in PolicyLayer and add a rule for configure_fastmail: 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 FastMail MCP Server. Nothing to install.

What risk level is configure_fastmail? +

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

Can I rate-limit configure_fastmail? +

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

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

configure_fastmail is provided by the FastMail MCP Server MCP server (jmhron/fastmailmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.