What is the difference between html and plain text email? Its all in the presentation. With html email the e mail content doesn't change but HTML enhances the visual impact and therefore has the potential to positively affect the usability experience of the e mail recipient.
HTML (Hypertext Markup Language) is a computer language that adds a variety of formatting capabilities to otherwise ordinary text. It is used extensively for creating Web pages. You are looking at HTML in action by viewing this web page. To see what HTML code looks like - from the View menu in your browser choose 'Page Source' and the on the page that displays you will recognize the text content of this page amongst additional bits of seemingly meaningless characters.
HTML allows greater display control eg colors, fancy fonts etc. So it follows that if you want fancy looking emails then HTML can be used - HTML emails will always be visually more pleasing than plain text emails. However there are other consideration to bear in mind not the least being the increased file size for an HTML email versus the plain text email equivalent. Another major consideration is the fact that exactly how the HTML email displays can depend on the email client used to view it. Unlike the one size fits all assurance of plain text e mail messages, with HTML e mails, you need to ensure compatibility across the spectrum of popular web clients. Some email clients might have elements eg Javascript turned off which would totally distort the display.
If you are in a market likely to be influenced by fancy graphic emails and there is evidence to suggest that the user will derive more pleasure from HTML emails then it is certainly worth a try providing that it is done properly. With Reply Focus you can use both html and plain text email.