Purpose: Send up to 100 transactional emails in one API call. Each item has the same fields as send-email (to, subject, text, from, etc.). NOT for: Sending one email (use send-email) or the same content to a segment (use create-broadcast + send-broadcast). When to use: User wants to send many ind...
AI agents invoke send-batch-emails to trigger actions in Email Sending MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool triggers external email delivery operations at scale — up to 100 emails per call. While it doesn't move money or destroy data, it executes real-world actions (sending emails) with significant blast radius: an AI agent could spam hundreds of recipients with malicious, embarrassing, or phishing content.
From the tool's definition Send up to 100 transactional emails in one API call. Each item has the same fields as send-email (to, subject, text, from, etc.).
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access send-batch-emails 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 send-batch-emails:
{
"version": "1",
"default": "deny",
"tools": {
"send-batch-emails": {
"limits": [
{
"counter": "send-batch-emails_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}send-batch-emails stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Purpose: Send up to 100 transactional emails in one API call. Each item has the same fields as send-email (to, subject, text, from, etc.). NOT for: Sending one email (use send-email) or the same content to a segment (use create-broadcast + send-broadcast). When to use: User wants to send many individual emails in bulk (e.g. 50 password resets, 100 receipts). Not for one-to-many broadcasts. It is categorised as a Execute tool in the Email Sending MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Email Sending MCP server in PolicyLayer and add a rule for send-batch-emails: 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.
send-batch-emails is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the send-batch-emails 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 send-batch-emails. 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.
send-batch-emails 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.