AI agents use send_email to create or update resources in Fastmail MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fastmail MCP Server environment.
Sending an email creates a new message and transmits it, which is a reversible write operation (emails can be deleted or unsent in many cases). However, the severity is high because an AI agent with this tool could send emails to arbitrary recipients with arbitrary content, enabling spam, phishing, impersonation, or social engineering attacks that may cause significant harm even if technically reversible.
From the tool's definition Tool name is 'send_email' with description 'Send an email'. The server description confirms it 'support[s] operations like sending emails'. This creates new email messages and sends them to recipients.
Documented attack patterns abuse exactly the kind of access send_email gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fastmail MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for send_email:
{
"version": "1",
"default": "deny",
"tools": {
"send_email": {
"limits": [
{
"counter": "send_email_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}send_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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Send an email. It is categorised as a Write tool in the Fastmail MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fastmail MCP Server MCP server in PolicyLayer and add a rule for send_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 Fastmail MCP Server. Nothing to install.
send_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 send_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 send_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.
send_email is provided by the Fastmail MCP Server MCP server (madllama25/fastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Fastmail MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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38 Fastmail MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.