Definitions for "HTML email"
It is now common for email publications to be available in both text and HTML (Hypertext Markup Language) formatting (a few, in fact, create HTML versions only). Unlike text email, HTML versions are relatively large in size and are thus slower to download, but they do offer graphics and images that text cannot, which is a valuable addition to some publications. Most email clients and web-based email services can read HTML email, though some earlier versions may not.
an email that contains text and graphics, usually presented in a nicely designed way
An email that is graphically rich with color and images and is emerging as the standard for email marketing. HTML messages often pull a higher response than plain-text messages.