Reschedule a scheduled email by updating its scheduled send time. Only works for emails that were scheduled and have not yet been sent.
AI agents use update-email to create or update resources in Email Sending MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Email Sending MCP environment.
This tool updates metadata (scheduled send time) of an email in reversible fashion. It does not execute a send operation, delete emails, or move money. The modification is reversible—the send time can be rescheduled again.
From the tool's definition Tool description states it 'Reschedule a scheduled email by updating its scheduled send time', which modifies the send time property of an existing scheduled email resource.
Documented attack patterns abuse exactly the kind of access update-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 update-email:
{
"version": "1",
"default": "deny",
"tools": {
"update-email": {
"limits": [
{
"counter": "update-email_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update-email 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.
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Reschedule a scheduled email by updating its scheduled send time. Only works for emails that were scheduled and have not yet been sent. It is categorised as a Write tool in the Email Sending MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Email Sending MCP server in PolicyLayer and add a rule for update-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.
update-email is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the update-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 update-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.
update-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.