HTML Mailer is a free Chrome add-on designed to enhance the Gmail email composition experience by allowing users to effortlessly insert custom HTML into their messages. This tool features a convenient HTML button in the compose toolbar, providing a large, distraction-free editor with a live preview that displays how the HTML will appear in the recipient's inbox. Users can swiftly insert their custom code with a single click, ensuring that their emails are not only visually appealing but also consistent with branding requirements.

This add-on is particularly beneficial for marketers, designers, and anyone seeking to create beautifully formatted emails. The clean and intuitive design caters to users of all skill levels, making it easy to include custom HTML elements such as tables and banners. Additionally, the secure nature of the tool ensures that email content remains within the browser, safeguarding user information while enhancing email composition.