AI agents use sendSimpleMail to create or update resources in Mail MCP Tool — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mail MCP Tool environment.
sendSimpleMail creates and sends emails, which is a reversible write operation (emails can be unsent or deleted). While the tool description is empty, the name and server context make the function clear. Severity is high because an AI agent could send malicious emails, spam, phishing messages, or commit social engineering attacks at scale with minimal friction.
From the tool's definition Tool name 'sendSimpleMail' and server description explicitly states it 'enabling AI models to access email services through standardized interfaces, allowing AI assistants to perform various email operations like sending emails'.
Documented attack patterns abuse exactly the kind of access sendSimpleMail gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mail MCP Tool, and nothing reaches the server without passing your rules. This is the rule we recommend for sendSimpleMail:
{
"version": "1",
"default": "deny",
"tools": {
"sendSimpleMail": {
"limits": [
{
"counter": "sendsimplemail_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}sendSimpleMail 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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sendSimpleMail. It is categorised as a Write tool in the Mail MCP Tool MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mail MCP Tool MCP server in PolicyLayer and add a rule for sendSimpleMail: 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 Mail MCP Tool. Nothing to install.
sendSimpleMail 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 sendSimpleMail 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 sendSimpleMail. 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.
sendSimpleMail is provided by the Mail MCP Tool MCP server (shuakami/mcp-mail). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 17 Mail MCP Tool tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
17 Mail MCP Tool tools catalogued and risk-classified — across an index of 42,500+ MCP servers.