HTML email

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).

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.

Since its conception, a number of people have vocally opposed all HTML email (and even MIME itself), for a variety of reasons. For instance, the ASCII Ribbon Campaign advocated that all email should be sent in ASCII text format. The campaign was unsuccessful and was abandoned in 2013. While still considered inappropriate in many newsgroup postings and mailing lists, its adoption for personal and business mail has only increased over time. Some of those who strongly opposed it when it first came out now see it as mostly harmless.

According to surveys by online marketing companies, adoption of HTML-capable email clients is now nearly universal, with less than 3% reporting that they use text-only clients. The majority of users prefer to receive HTML emails over plain text.

Email software that complies with RFC 2822 is only required to support plain text, not HTML formatting. Sending HTML formatted emails can therefore lead to problems if the recipient's email client does not support it. In the worst case, the recipient will see the HTML code instead of the intended message.

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