create_alias · TrekMail MCP Server MCP: Risk & Policy

WHAT IT DOES

What create_alias does on TrekMail MCP Server

AI agents use create_alias 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 create_alias needs a policy

This tool creates a new email alias, which is a reversible modification to email infrastructure. It does not execute arbitrary code, delete data, move money, or retrieve sensitive information. The severity is medium because creating unauthorized aliases could enable email spoofing or unauthorized sending, but the impact is limited to alias configuration and can be undone.

From the tool's definition Tool description states 'Add a new email alias to a mailbox' and 'Optionally allow sending from this alias address', indicating creation of new email configuration that modifies mailbox settings.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_alias Rate-limited

create_alias 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": {
    "create_alias": {
      "limits": [
        {
          "counter": "create_alias_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 create_alias

What does the create_alias tool do? +

Add a new email alias to a mailbox. The alias delivers mail into the same mailbox — no separate login needed. Optionally allow sending from this alias address. Requires Starter plan or above. Use list_domains to find domain IDs. 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 create_alias? +

Register the TrekMail MCP Server MCP server in PolicyLayer and add a rule for create_alias: 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 create_alias? +

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

Can I rate-limit create_alias? +

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

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

create_alias 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.