AI agents call mail_list_messages to retrieve information from M365 without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and queries email metadata (subject, sender, date, preview) without side effects. It fits the Read category as it only fetches information. Severity is medium because email messages often contain sensitive personal, financial, or confidential business information; unauthorized listing could expose PII or trade secrets, but the tool itself only retrieves metadata, not full message bodies or…
From the tool's definition Tool name 'mail_list_messages' and description indicate it 'List email messages from a Microsoft 365 mailbox. Returns subject, sender, date, and preview' — pure data retrieval with no modification or deletion.
Attacks that exploit this kind of access
List email messages from a Microsoft 365 mailbox. Returns subject, sender, date, and preview. Use. It is categorised as a Read tool in the M365 MCP Server, which means it retrieves data without modifying state.
Register the M365 MCP server in PolicyLayer and add a rule for mail_list_messages: 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 M365. Nothing to install.
mail_list_messages is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the mail_list_messages 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 mail_list_messages. 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.
mail_list_messages is provided by the M365 MCP server (swamirama/m365-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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