Ellie is a software tool that claims to craft replies to emails as if they were written by the user. It uses GPT-4, a powerful AI technology, to learn the user's writing style and generate personalized replies. It is available as a Chrome or Firefox Extension, and promises to never share, sell, or do anything shady with user data. According to the website, it is best for automatically generating personalized replies to emails in the same writing style as the user, allowing for quick and accurate communication. Some users may find that it is a great tool for lawyers, sales professionals, and teachers to quickly generate emails, saving them time and energy. It may differentiate itself from other software competitors due to its AI-powered functionality and its promise of secure and private communication.