update_mail_rule · TrekMail MCP Server MCP: Risk & Policy

WHAT IT DOES

What update_mail_rule does on TrekMail MCP Server

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

WHY IT NEEDS A POLICY

Why update_mail_rule needs a policy

This tool modifies existing mail filter rules, which is a Write operation (reversible change to data). It does not delete rules (Destructive), execute arbitrary code (Execute), or move money (Financial). Severity is medium because misconfiguration of mail filters could cause emails to be misrouted or blocked, affecting email delivery and user productivity, but the change can be undone by updating the rule again.

From the tool's definition Tool description states "Update an existing mail filter" - the word "Update" indicates reversible modification of data (mail filter configuration).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_mail_rule Rate-limited

update_mail_rule 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": {
    "update_mail_rule": {
      "limits": [
        {
          "counter": "update_mail_rule_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 TrekMail MCP Server, so you can run agents against it safely.

FAQ

Questions about update_mail_rule

What does the update_mail_rule tool do? +

Update an existing mail filter. Pro and Agency plans only. It is categorised as a Write tool in the TrekMail 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 update_mail_rule? +

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

What risk level is update_mail_rule? +

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

Can I rate-limit update_mail_rule? +

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

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

update_mail_rule is provided by the TrekMail MCP Server MCP server (trekmail/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.