HTML email
（重定向自HTML mail）
HTML email is the use of a subset of HTML to provide formatting and semantic markup capabilities in email that are not available with plain text: Text can be linked without displaying a URL, or breaking long URLs into multiple pieces. Text is wrapped to fit the width of the viewing window, rather than uniformly breaking each line at 78 characters (defined in RFC 5322, which was necessary on older text terminals). It allows in-line inclusion of images, tables, as well as diagrams or mathematical formulae as images, which are otherwise difficult to convey (typically using ASCII art).