block_sender · TrekMail MCP Server MCP: Risk & Policy

WHAT IT DOES

What block_sender does on TrekMail MCP Server

AI agents use block_sender 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 block_sender needs a policy

This tool modifies email filtering configuration by creating block rules, which is a reversible write operation. The effect is not destructive (rules can be unblocked), nor does it execute arbitrary code or move financial assets. While blocking senders affects email delivery behavior, the action itself is a configuration write that persists blocking metadata.

From the tool's definition Tool description states 'Block an email address or entire domain' which creates a blocking rule that modifies mailbox configuration settings.

Risk signalsBulk/mass operation — affects multiple targets

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

block_sender Rate-limited

block_sender 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": {
    "block_sender": {
      "limits": [
        {
          "counter": "block_sender_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 block_sender

What does the block_sender tool do? +

Block an email address (e.g. spammer@evil.com) or entire domain (e.g. @evil.com). Max 50 per mailbox. 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 block_sender? +

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

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

Can I rate-limit block_sender? +

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

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

block_sender 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.