Cancel a scheduled email that has not yet been sent. Only works for emails that were scheduled using the scheduledAt parameter.
AI agents call cancel-email to permanently remove resources in Email Sending MCP — typically in cleanup and lifecycle workflows. It does its job in a single call, and there is no undo.
Cancelling a scheduled email is an irreversible action — once cancelled, that scheduled send is permanently aborted and cannot be undone. It does not merely modify the email but permanently removes the pending send operation. Severity is medium because it affects only a single scheduled email with no data deletion or financial impact, but misuse by an AI agent could silently prevent intended communications.
From the tool's definition Cancel a scheduled email that has not yet been sent
Documented attack patterns abuse exactly the kind of access cancel-email gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Email Sending MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for cancel-email:
{
"version": "1",
"default": "deny",
"hide": [
"cancel-email"
]
}cancel-email disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.
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Cancel a scheduled email that has not yet been sent. Only works for emails that were scheduled using the scheduledAt parameter. It is categorised as a Destructive tool in the Email Sending MCP MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.
Register the Email Sending MCP server in PolicyLayer and add a rule for cancel-email: 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 Email Sending MCP. Nothing to install.
cancel-email 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 cancel-email 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 cancel-email. 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.
cancel-email is provided by the Email Sending MCP server (resend/resend-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 77 Email Sending MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
77 Email Sending MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.