AI agents use reply-to-message to create or update resources in Apple Mail — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Apple Mail environment.
This tool creates and sends a new email message as a reply, which is a reversible write operation that modifies mailbox state and external email recipients' inboxes. It does not delete data (Destructive), execute arbitrary code (Execute), or move money (Financial).
From the tool's definition Tool name 'reply-to-message' combined with server description stating it 'send, search, and manage emails in Apple Mail'.
Documented attack patterns abuse exactly the kind of access reply-to-message gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Apple Mail, and nothing reaches the server without passing your rules. This is the rule we recommend for reply-to-message:
{
"version": "1",
"default": "deny",
"tools": {
"reply-to-message": {
"limits": [
{
"counter": "reply-to-message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}reply-to-message 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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reply-to-message. It is categorised as a Write tool in the Apple Mail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Apple Mail MCP server in PolicyLayer and add a rule for reply-to-message: 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 Apple Mail. Nothing to install.
reply-to-message 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 reply-to-message 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 reply-to-message. 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.
reply-to-message is provided by the Apple Mail MCP server (sweetrb/apple-mail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 40 Apple Mail tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
40 Apple Mail tools catalogued and risk-classified — across an index of 42,500+ MCP servers.