The standardization of email address space and ability to reach majority of people was great. I wonder if anything else good has happened to email since 1971. Email becomes harder and harder to use with the spread of broken mail user agents and bad habits. Sending messages in such a way that everybody can easily read, index, browse, and store them is a good goal to pursue.
Quoted text appears with a greater than sign in the beginning of each line.
Quoting complete messages is usually unnecessary. If your recipient wants to read the message to which you are replying they can do just that . A few sentences to which you are writing a direct reply or simply a sentence or two to provide context is enough. If several sentences need to be quoted to make clear to what you're replying, but they are separated with text you don't wish to include, a common practice is to elide them by replacing them with an ellipsis in brackets. HTML isn't plain text.