Set default_outbound_mailbox_id and/or auth_sender_mailbox_id for a project. Use list_mailboxes first to choose an explicit mailbox id; sending without a mailbox uses the configured outbound default instead of guessing.
AI agents use set_mailbox_defaults to create or update resources in Run402 — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Run402 environment.
This tool creates or modifies project-level configuration data (mailbox defaults) in a reversible manner. It changes email routing and authentication behavior but does not delete data, execute arbitrary code, move money, or cause irreversible harm.
From the tool's definition Tool description states 'Set default_outbound_mailbox_id and/or auth_sender_mailbox_id for a project', which are configuration changes that modify project settings.
Attacks that exploit this kind of access
Set default_outbound_mailbox_id and/or auth_sender_mailbox_id for a project. Use list_mailboxes first to choose an explicit mailbox id; sending without a mailbox uses the configured outbound default instead of guessing. It is categorised as a Write tool in the Run402 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Run402 MCP server in PolicyLayer and add a rule for set_mailbox_defaults: 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 Run402. Nothing to install.
set_mailbox_defaults 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 set_mailbox_defaults 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 set_mailbox_defaults. 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.
set_mailbox_defaults is provided by the Run402 MCP server (kychee-com/run402). 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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