Download an email attachment by UID and part ID. Returns base64-encoded content.
AI agents call mail_attachment to retrieve information from Shellgate without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool retrieves and returns attachment content without creating, modifying, deleting, or executing anything. It is purely informational with minimal blast radius—an AI agent downloading attachments cannot cause irreversible harm or execute code through this operation alone. The base64 encoding is simply a safe transport mechanism for binary content.
From the tool's definition Tool name 'mail_attachment' and description 'Download an email attachment by UID and part ID. Returns base64-encoded content.' indicate a retrieval operation with no modification or deletion of data.
Documented attack patterns abuse exactly the kind of access mail_attachment gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Shellgate, and nothing reaches the server without passing your rules. This is the rule we recommend for mail_attachment:
{
"version": "1",
"default": "deny",
"tools": {
"mail_attachment": {}
}
}mail_attachment is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Download an email attachment by UID and part ID. Returns base64-encoded content. It is categorised as a Read tool in the Shellgate MCP Server, which means it retrieves data without modifying state.
Register the Shellgate MCP server in PolicyLayer and add a rule for mail_attachment: 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 Shellgate. Nothing to install.
mail_attachment 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_attachment 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_attachment. 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_attachment is provided by the Shellgate MCP server (matthiastjong/shellgate). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Shellgate, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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31 Shellgate tools catalogued and risk-classified — across an index of 43,000+ MCP servers.