update_mailbox · TrekMail MCP Server MCP: Risk & Policy

WHAT IT DOES

What update_mailbox does on TrekMail MCP Server

AI agents use update_mailbox 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_mailbox needs a policy

The tool creates or modifies mailbox data (display_name field) in a reversible manner, fitting the Write category. Severity is medium because unauthorized modification of display names could be used for spoofing/impersonation attacks or to disrupt email communications, but the scope is limited to non-critical metadata and the change can be undone.

From the tool's definition Tool description explicitly states 'Update write-safe fields on a mailbox' and 'supports display_name'; this is a reversible modification of mailbox metadata (the From header display name), not deletion or code execution.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_mailbox Rate-limited

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

FAQ

Questions about update_mailbox

What does the update_mailbox tool do? +

Update write-safe fields on a mailbox. Currently supports display_name (used in the From header of outbound mail). Does NOT touch identity (address/local_part), password, storage, or domain — use the dedicated endpoints for those. 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_mailbox? +

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

What risk level is update_mailbox? +

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

Can I rate-limit update_mailbox? +

Yes. Add a rate_limit block to the update_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 update_mailbox completely? +

Set action: deny in the PolicyLayer policy for update_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 update_mailbox? +

update_mailbox 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.