Reply to all recipients of an existing email
AI agents use outlook_reply_all to create or update resources in Outlook — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Outlook environment.
This tool sends an email reply to all recipients of an existing message. It creates new email communications (Write), but the blast radius is high because an AI agent could inadvertently reply-all to large distribution lists, exposing sensitive information or spamming many recipients.
From the tool's definition Reply to all recipients of an existing email
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access outlook_reply_all gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Outlook, and nothing reaches the server without passing your rules. This is the rule we recommend for outlook_reply_all:
{
"version": "1",
"default": "deny",
"tools": {
"outlook_reply_all": {
"limits": [
{
"counter": "outlook_reply_all_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}outlook_reply_all 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 all recipients of an existing email. It is categorised as a Write tool in the Outlook MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Outlook MCP server in PolicyLayer and add a rule for outlook_reply_all: 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 Outlook. Nothing to install.
outlook_reply_all 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 outlook_reply_all 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 outlook_reply_all. 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.
outlook_reply_all is provided by the Outlook MCP server (xenoxilus/outlook-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Outlook, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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43 Outlook tools catalogued and risk-classified — across an index of 43,000+ MCP servers.