Open Mail CLI – Agent Email Toolkit

This skill equips the agent with a full-featured email client accessible via the mail-cli command. The agent can send, receive, search, organize, and automate emails entirely from the terminal through IMAP/SMTP protocols, with offline-first local storage. It also provides a local HTTP API server for programmatic integration.

Installation

npm install -g open-mail-cli
# Requirements: Node.js >= 18.0.0

Getting Started

1. Configure an Email Account

# Interactive wizard (recommended)
mail-cli config

# Or manual setup
mail-cli account add --email user@gmail.com --name "My Gmail" \
  --imap-host imap.gmail.com --imap-port 993 \
  --smtp-host smtp.gmail.com --smtp-port 465 \
  --username user@gmail.com --password "app-password" --test

2. Sync, Read, and Send

mail-cli sync                # Fetch emails from server
mail-cli list --unread       # Browse unread emails
mail-cli list --format json --fields id,subject,from  # Structured output for parsing
mail-cli read <email-id>     # Read a specific email
mail-cli send --to user@example.com --subject "Hello" --body "Content"

Capabilities Overview

Choose the reference that matches the task at hand. Each reference includes purpose, scenarios, best practices, and full command syntax.

Output Control & Error Handling

Reference: references/output-and-errors.md

Control output format (--format json/markdown/html), select specific fields (--fields), and handle errors via standardized exit codes and JSON error output. Use this when the agent needs to parse command output programmatically or handle failures gracefully.

Webhooks & HTTP API

Reference: references/webhooks-and-api.md

Register webhooks for email events, trigger scripts on new mail, and use the local HTTP API server with OpenAPI documentation. Use this when the agent needs real-time event-driven workflows or REST API integration.

Sending & Composing

Reference: references/sending-and-replying.md

Send emails, reply to conversations, forward messages, and manage drafts. Use this when the user needs to compose or respond to emails.

Reading & Searching

Reference: references/reading-and-searching.md

List, filter, read, and search emails. View conversations as threads. Use this when the user wants to check inbox, find specific emails, or follow a conversation.

Organization

Reference: references/organization.md

Organize emails with tags, folders, stars, flags, and trash management. Use this when the user wants to categorize, prioritize, or clean up their mailbox.

Accounts & Sync

Reference: references/accounts-and-sync.md

Manage multiple email accounts, configure IMAP/SMTP, run background sync daemon. Includes provider settings table (Gmail, Outlook, QQ Mail, etc.) and troubleshooting. Use this for setup, connectivity issues, or multi-account workflows.

Automation

Reference: references/automation.md

Email templates with variables, signatures, desktop notifications, spam filtering, contact management, and import/export. Use this when the user wants to automate repetitive email tasks or manage contacts and spam.

Key Principles

• Sync before read: Local storage is offline-first. Always mail-cli sync before listing or searching if fresh data is expected.
• Confirm before send: Always verify recipient, subject, and content with the user before executing send, reply, or forward.
• Non-destructive by default: delete moves to trash. Only use --permanent when the user explicitly requests irreversible deletion.
• Use --yes for automation: Skip interactive confirmation prompts in automated workflows.
• Use --format json for parsing: When the agent needs to parse output programmatically, use JSON format. Use --format markdown when output is consumed by an LLM.
• Use --fields to reduce noise: Request only the fields needed (e.g. --fields id,subject,from) to keep output focused and reduce token usage.
• Check exit codes for error handling: Exit codes indicate error category (0=success, 1=general, 2=validation, 3=network, 4=auth). Branch logic based on exit code instead of parsing error text.
• Templates over repetition: If the user sends similar emails more than twice, create a template.
• Tags for cross-cutting, folders for exclusive: An email can have multiple tags but belongs to one folder.