HTML Graphical emails is the use of a subset of HTML to provide formatting and semantic markup capabilities in email that are not available with plain text.
Most graphical email clients support HTML email, and many default to it. Many of these clients include both a GUI editor for composing HTML emails and a rendering engine for displaying received HTML emails.
HTML Graphical mail allows the sender to properly express quotations, headings, bulleted lists, emphasized text, subscripts and superscripts, and other visual and typographic cues to improve the readability and aesthetics of the message, as well as semantic information encoded within the message, such as the original author and Message-ID of a quote. It allows in-line inclusion of tables, as well as diagrams or mathematical formulae as images, which are otherwise difficult to convey through standard emails.