Remove a sender from the blocked list. Requires TREKMAIL_ALLOW_DESTRUCTIVE=true.
AI agents call unblock_sender to permanently remove resources in TrekMail MCP Server — typically in cleanup and lifecycle workflows. It does its job in a single call, and there is no undo.
While unblocking a sender is not data deletion, it irreversibly removes a security control (the block) and is explicitly gated behind a DESTRUCTIVE flag by the server itself. This indicates the authors consider it a destructive operation. Misuse could expose users to previously blocked malicious senders, giving it medium severity.
From the tool's definition 'Remove a sender from the blocked list' and 'Requires TREKMAIL_ALLOW_DESTRUCTIVE=true'
Attacks that exploit this kind of access
Remove a sender from the blocked list. Requires TREKMAIL_ALLOW_DESTRUCTIVE=true. It is categorised as a Destructive tool in the TrekMail MCP Server MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.
Register the TrekMail MCP Server MCP server in PolicyLayer and add a rule for unblock_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.
unblock_sender is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the unblock_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.
Set action: deny in the PolicyLayer policy for unblock_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.
unblock_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.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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