agentmail

name	agentmail
description	Give the agent its own dedicated email inbox via AgentMail. Send, receive, and manage email autonomously using agent-owned email addresses (e.g. [e-mail]).
version	1.0.0
platforms	["linux","macos","windows"]
metadata	{"cast":{"tags":["email","communication","agentmail","mcp"],"category":"email"}}

AgentMail — Agent-Owned Email Inboxes

Requirements

• AgentMail API key (required) — sign up at https://console.agentmail.to (free tier: 3 inboxes, 3,000 emails/month; paid plans from $20/mo)
• Node.js 18+ (for the MCP server)

When to Use

Use this skill when you need to:

• Give the agent its own dedicated email address
• Send emails autonomously on behalf of the agent
• Receive and read incoming emails
• Manage email threads and conversations
• Sign up for services or authenticate via email
• Communicate with other agents or humans via email

This is NOT for reading the user's personal email (use himalaya or Gmail for that). AgentMail gives the agent its own identity and inbox.

Setup

1. Get an API Key

• Go to https://console.agentmail.to
• Create an account and generate an API key (starts with am_)

2. Configure MCP Server

Add to ~/.cast/config.yaml (paste your actual key — MCP env vars are not expanded from .env):

mcp_servers:
  agentmail:
    command: "npx"
    args: ["-y", "agentmail-mcp"]
    env:
      AGENTMAIL_API_KEY: "am_your_key_here"

3. Restart Cast

cast

All 11 AgentMail tools are now available automatically.

Available Tools (via MCP)

Tool	Description
list_inboxes	List all agent inboxes
get_inbox	Get details of a specific inbox
create_inbox	Create a new inbox (gets a real email address)
delete_inbox	Delete an inbox
list_threads	List email threads in an inbox
get_thread	Get a specific email thread
send_message	Send a new email
reply_to_message	Reply to an existing email
forward_message	Forward an email
update_message	Update message labels/status
get_attachment	Download an email attachment

Procedure

Create an inbox and send an email

1. Create a dedicated inbox:
   • Use create_inbox with a username (e.g. cast-agent)
   • The agent gets address: [e-mail]
2. Send an email:
   • Use send_message with inbox_id, to, subject, text
3. Check for replies:
   • Use list_threads to see incoming conversations
   • Use get_thread to read a specific thread

Check incoming email

1. Use list_inboxes to find your inbox ID
2. Use list_threads with the inbox ID to see conversations
3. Use get_thread to read a thread and its messages

Reply to an email

1. Get the thread with get_thread
2. Use reply_to_message with the message ID and your reply text

Example Workflows

Sign up for a service:

1. create_inbox (username: "signup-bot")
2. Use the inbox address to register on the service
3. list_threads to check for verification email
4. get_thread to read the verification code

Agent-to-human outreach:

1. create_inbox (username: "cast-outreach")
2. send_message (to: [e-mail], subject: "Hello", text: "...")
3. list_threads to check for replies

Pitfalls

• Free tier limited to 3 inboxes and 3,000 emails/month
• Emails come from @agentmail.to domain on free tier (custom domains on paid plans)
• Node.js (18+) is required for the MCP server (npx -y agentmail-mcp)
• The mcp Python package must be installed: pip install mcp
• Real-time inbound email (webhooks) requires a public server — use list_threads polling via cronjob instead for personal use

Verification

After setup, test with:

cast --toolsets mcp -q "Create an AgentMail inbox called test-agent and tell me its email address"

You should see the new inbox address returned.

References

• AgentMail docs: https://docs.agentmail.to/
• AgentMail console: https://console.agentmail.to
• AgentMail MCP repo: https://github.com/agentmail-to/agentmail-mcp
• Pricing: https://www.agentmail.to/pricing