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. This integration gives your agent its own email inbox to send, receive, and reply to messages using natural language, with SPF/DKIM-verified inbound mail and optional human-in-the-loop approval on outbound messages.

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+ (only required for the local 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,
                ),
            )
        ],
    )
    ```

=== "Remote 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 (
        StreamableHTTPConnectionParams,
    )

    E2A_API_KEY = "YOUR_E2A_API_KEY"

    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=StreamableHTTPConnectionParams(
                    url="https://mcp.e2a.dev/mcp",
                    headers={"Authorization": f"Bearer {E2A_API_KEY}"},
                    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 };
    ```

=== "Remote MCP Server"

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

    const E2A_API_KEY = "YOUR_E2A_API_KEY";

    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: "StreamableHTTPConnectionParams",
                url: "https://mcp.e2a.dev/mcp",
                transportOptions: {
                    requestInit: {
                        headers: {
                            Authorization: `Bearer ${E2A_API_KEY}`,
                        },
                    },
                },
            }),
        ],
    });

    export { rootAgent };
    ```

Available tools

Identity

Tool	Description
whoami	Return the default agent's full record (requires E2A_AGENT_EMAIL when the account has more than one agent)
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 and no webhook is required
update_agent	Update an existing agent's webhook URL, mode, or HITL setting
delete_agent	Permanently delete an agent (requires confirm: true) and stop accepting mail for that address

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

Agents created with `agent_mode: "cloud"` receive mail via webhooks instead
of polling. Your webhook handler must verify the HMAC signature on every
delivery. See the [cloud-mode webhook
example](https://github.com/Mnexa-AI/e2a/tree/main/examples/adk-cloud-webhook)
for a complete setup with signature verification.

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
get_attachment_data	Download an attachment's bytes by message id and 0-based attachment index (returned as base64)

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

Domains

Tool	Description
list_domains	List every custom domain registered to the authenticated user, with verification state
register_domain	Add a custom domain and receive the DNS records needed to prove ownership
verify_domain	Re-run DNS verification on a registered domain after the records are in place
delete_domain	Remove a custom domain (requires confirm: true; agents on the shared domain are unaffected)

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 need to specify it on every call
E2A_BASE_URL	No	https://e2a.dev	Self-hosted deployment URL (local MCP server only)

Additional resources

• e2a MCP Server source
• Runnable ADK example
• Cloud-mode webhook example
• e2a documentation
• npm package