This guide covers building HTML emails using Ruby on Rails and Tailwind CSS. It discusses how to overcome common obstacles such as Gmail message clipping, large file size, Apple autolinking, and more. The article provides a step-by-step approach to setting up the necessary tools and configuring PostCSS for email. It also covers how to create an email-specific stylesheet using Tailwind CSS and how to implement inline styles using a library called Roadie. Additionally, it discusses how to accommodate Gmail desktop styles and test emails on different platforms. The guide aims to provide a reference for those exploring how to build HTML emails in their own application using Rails and Tailwind.