email-delivability-audit: Four DNS Gates Before Sending Mail

This plugin is an online tool for intelligently auditing recipient addresses before email sending, preventing bounce-related damage to domain reputation. It determines address deliverability through four sequential DNS gates (format, dead domains, MX records, role/placeholder) and outputs a result of `sendable`, `risky`, or `dead`. The plugin supports CSV batch processing, and its results are traceable to actual DNS queries rather than guesses. It supports platforms such as Claude Code and DSH, relies on `dig` or Python libraries to run, objectively verifies address validity, and helps prevent invalid addresses from affecting email delivery.