Send emails in bulk to multiple recipients with rate limiting
AI agents use send-bulk-emails to create or update resources in SMTP MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your SMTP MCP Server environment.
This tool creates and sends emails to multiple recipients, which is a write operation that modifies external state (recipient inboxes) and can have significant side effects (spam, phishing, business disruption).
From the tool's definition Tool description states it can 'Send emails in bulk to multiple recipients' - a write operation that creates/sends messages at scale. The rate limiting qualifier does not change the fundamental nature of the action.
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access send-bulk-emails gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and SMTP MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for send-bulk-emails:
{
"version": "1",
"default": "deny",
"tools": {
"send-bulk-emails": {
"limits": [
{
"counter": "send-bulk-emails_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}send-bulk-emails 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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Send emails in bulk to multiple recipients with rate limiting. It is categorised as a Write tool in the SMTP MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the SMTP MCP Server MCP server in PolicyLayer and add a rule for send-bulk-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 SMTP MCP Server. Nothing to install.
send-bulk-emails 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 send-bulk-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-bulk-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-bulk-emails is provided by the SMTP MCP Server MCP server (samihalawa/mcp-server-smtp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from SMTP MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
11 SMTP MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.