ReplaiGPT is an AI-powered email reply tool that generates personalized responses using predefined context. It integrates seamlessly with Gmail and supports multiple languages. The tool allows users to create and save information about themselves or their business, which can be used as context for generating customized email replies. It is designed to handle recurring email requests and is privacy-friendly, as emails and contexts are not saved on external servers. ReplaiGPT offers a basic version that is free to use and requires users to provide their own OpenAI API key.