mail_create_mailbox · Pyfastmail MCP: Risk & Policy

WHAT IT DOES

What mail_create_mailbox does on Pyfastmail

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

WHY IT NEEDS A POLICY

Why mail_create_mailbox needs a policy

The tool creates a new mailbox, which is a reversible write operation that modifies the email account structure. It is not a read-only operation (no query/fetch semantics), not immediately destructive (mailbox can be deleted), and not financial.

From the tool's definition Tool name 'mail_create_mailbox' indicates creation of a new mailbox/folder. Combined with server description stating it provides 'full access to Fastmail accounts for managing email', this is a write operation that creates a new email organizational structure.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mail_create_mailbox Rate-limited

mail_create_mailbox 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_create_mailbox": {
      "limits": [
        {
          "counter": "mail_create_mailbox_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 Pyfastmail, so you can run agents against it safely.

FAQ

Questions about mail_create_mailbox

What does the mail_create_mailbox tool do? +

mail_create_mailbox. It is categorised as a Write tool in the Pyfastmail 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_create_mailbox? +

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

What risk level is mail_create_mailbox? +

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

Can I rate-limit mail_create_mailbox? +

Yes. Add a rate_limit block to the mail_create_mailbox 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_create_mailbox completely? +

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

mail_create_mailbox is provided by the Pyfastmail MCP server (pjosols/pyfastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.