send_email · FastMail MCP Server MCP: Risk & Policy

WHAT IT DOES

What send_email does on FastMail MCP Server

AI agents use send_email 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 send_email needs a policy

The tool creates new email messages, which is a Write operation (creates data reversibly). It is not Execute because it doesn't run arbitrary code or scripts—it performs a scoped action. It is not Financial despite touching email communication, as sending email itself carries no monetary obligation.

From the tool's definition Tool name 'send_email' and description 'Send an email through FastMail' directly indicate creation of new messages. The sibling tool context (reading emails, searching, managing folders) confirms this is a reversible write operation within an email system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_email Rate-limited

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

FAQ

Questions about send_email

What does the send_email tool do? +

Send an email through FastMail. 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 send_email? +

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

What risk level is send_email? +

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

Can I rate-limit send_email? +

Yes. Add a rate_limit block to the send_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 send_email completely? +

Set action: deny in the PolicyLayer policy for send_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 send_email? +

send_email 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.