google__adk-docs/docs/integrations/e2a.md

catalog_title, catalog_description, catalog_icon, catalog_tags

catalog_title	catalog_description	catalog_icon	catalog_tags
e2a	Authenticated email gateway for AI agents with human-in-the-loop approval	/integrations/assets/e2a.png	mcp

e2a MCP tool for ADK

Supported in ADKPythonTypeScript

The e2a MCP Server connects your ADK agent to e2a, an authenticated email gateway built for AI agents. Inbound mail is SPF/DKIM-verified before it reaches your agent. Outbound mail can be held for human approval before it ships.

Use cases

• Give agents their own inboxes: Provision dedicated email addresses (e.g. support-bot@your-domain.com) and let agents send and receive mail just like a teammate.

• Authenticated inbound: Every incoming message arrives with SPF and DKIM verification results so your agent knows whether the sender is who they claim to be.

• Human-in-the-loop approval: Configure HITL on any agent and outbound messages are held in a pending queue until a reviewer approves them — optionally with edits to subject, body, or recipients before sending.

• Automate threaded conversations: Reply to received emails with proper In-Reply-To and References headers preserved, so threads stay intact across multiple turns.

Prerequisites

• A free e2a account and an API key from the dashboard.
• Node.js 18+ on the machine running the agent (the MCP server is distributed via npx -y @e2a/mcp-server).

Use with agent

=== "Python"

=== "Local MCP Server"

    ```python
    from google.adk.agents import Agent
    from google.adk.tools.mcp_tool import McpToolset
    from google.adk.tools.mcp_tool.mcp_session_manager import StdioConnectionParams
    from mcp import StdioServerParameters

    E2A_API_KEY = "YOUR_E2A_API_KEY"
    E2A_AGENT_EMAIL = "your-bot@your-domain.com"  # optional default inbox

    root_agent = Agent(
        model="gemini-flash-latest",
        name="e2a_agent",
        instruction=(
            "You manage email through the e2a tools. Call whoami once "
            "to find your inbox address. Use list_messages and "
            "get_message to read; use reply_to_message (not "
            "send_email) when replying to an existing thread so "
            "threading headers are preserved."
        ),
        tools=[
            McpToolset(
                connection_params=StdioConnectionParams(
                    server_params=StdioServerParameters(
                        command="npx",
                        args=["-y", "@e2a/mcp-server"],
                        env={
                            "E2A_API_KEY": E2A_API_KEY,
                            "E2A_AGENT_EMAIL": E2A_AGENT_EMAIL,
                        },
                    ),
                    timeout=30,
                ),
            )
        ],
    )
    ```

=== "TypeScript"

=== "Local MCP Server"

    ```typescript
    import { LlmAgent, MCPToolset } from "@google/adk";

    const E2A_API_KEY = "YOUR_E2A_API_KEY";
    const E2A_AGENT_EMAIL = "your-bot@your-domain.com"; // optional default inbox

    const rootAgent = new LlmAgent({
        model: "gemini-flash-latest",
        name: "e2a_agent",
        instruction:
            "You manage email through the e2a tools. Call whoami once " +
            "to find your inbox address. Use list_messages and " +
            "get_message to read; use reply_to_message (not " +
            "send_email) when replying to an existing thread so " +
            "threading headers are preserved.",
        tools: [
            new MCPToolset({
                type: "StdioConnectionParams",
                serverParams: {
                    command: "npx",
                    args: ["-y", "@e2a/mcp-server"],
                    env: {
                        E2A_API_KEY: E2A_API_KEY,
                        E2A_AGENT_EMAIL: E2A_AGENT_EMAIL,
                    },
                },
            }),
        ],
    });

    export { rootAgent };
    ```

Available tools

Identity

Tool	Description
whoami	Return the default agent's full record (requires E2A_AGENT_EMAIL)
list_agents	List every agent inbox owned by the authenticated user
create_agent	Register a new inbox using a slug on the shared domain; defaults to local mode so the agent receives mail by polling — no webhook required

!!! warning "Cloud-mode agents must verify webhook signatures"

When you create an agent with `agent_mode: "cloud"`, e2a HMAC-signs every
webhook delivery against your account's webhook signing secret
(`E2A_WEBHOOK_SECRET`, shown in the [e2a dashboard](https://e2a.dev)).
Your webhook handler must verify the signature on every request —
the e2a SDK exposes `parseWebhook(body, secret)` which parses and
verifies in one call. Local-mode agents (the default) avoid this
entirely by polling via `list_messages`. A complete runnable
cloud-mode + ADK example with proper signature verification lives
at [github.com/Mnexa-AI/e2a/tree/main/examples/adk-cloud-webhook](https://github.com/Mnexa-AI/e2a/tree/main/examples/adk-cloud-webhook).

Messages

Tool	Description
send_email	Send a new email; returns status: pending_approval instead of sent when HITL is enabled
reply_to_message	Reply to an inbound message; preserves In-Reply-To and References headers
list_messages	List inbound mail with status filter (unread / read / all) and pagination
get_message	Fetch full body, headers, and attachment metadata for one message

Human-in-the-loop approval

Tool	Description
list_pending_messages	List outbound mail awaiting human approval, soonest-expiring first
get_pending_message	Get the full draft (subject, recipients, body) of a pending message
approve_pending_message	Send a held message, optionally with reviewer edits (subject / body / recipients)
reject_pending_message	Discard a held message; optional reason stored for audit

Configuration

Variable	Required	Default	Description
E2A_API_KEY	Yes	—	Your e2a API key
E2A_AGENT_EMAIL	No	—	Default agent inbox; scopes tools so the LLM doesn't repeat the address on every call
E2A_BASE_URL	No	https://e2a.dev	Self-hosted deployment URL

Additional resources

• e2a MCP Server source
• Runnable ADK example
• e2a documentation
• npm package