mail_update_masked_email · Pyfastmail MCP: Risk & Policy

WHAT IT DOES

What mail_update_masked_email does on Pyfastmail

AI agents use mail_update_masked_email 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_update_masked_email needs a policy

This tool modifies email masking settings (a configuration feature in Fastmail that creates masked/alias email addresses), which is a Write operation—reversible changes to account data. While potentially sensitive as it affects email privacy controls, it is not Destructive (data can be modified back), Financial (no money movement), or Execute (no arbitrary code/command execution).

From the tool's definition Tool name 'mail_update_masked_email' indicates modification of email masking settings. Server description states it 'provides AI assistants with full access to Fastmail accounts for managing email' and implements tools 'to enable comprehensive account…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mail_update_masked_email Rate-limited

mail_update_masked_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": {
    "mail_update_masked_email": {
      "limits": [
        {
          "counter": "mail_update_masked_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 Pyfastmail, so you can run agents against it safely.

FAQ

Questions about mail_update_masked_email

What does the mail_update_masked_email tool do? +

mail_update_masked_email. 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_update_masked_email? +

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

What risk level is mail_update_masked_email? +

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

Can I rate-limit mail_update_masked_email? +

Yes. Add a rate_limit block to the mail_update_masked_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 mail_update_masked_email completely? +

Set action: deny in the PolicyLayer policy for mail_update_masked_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 mail_update_masked_email? +

mail_update_masked_email 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.