HTML e-mail

HTML e-mail is the most popular method to format e-mail messages, and uses HTML.

While most e-mail clients support HTML e-mail, the level of support is even more diverse than among web browsers. The situation gets even more complicated by web-based e-mail clients like Gmail and Hotmail, where first the HTML e-mail source is transformed into an HTML snippet that is inserted into the HTML source of the e-mail client, and secondly the web browser (or other user agent) renders the HTML page.

Creating HTML e-mail
While most e-mail clients provide a graphical interface to create HTML e-mail, there are few that allow full control over the HTML source. One of the most direct ways is using the command-line to telnet to the mail server (the provided server replies are examples, they don't need to be exactly the same):