One of the primary reasons email sucks is the allowance of "text/html" with no text/plain part, or worse, something like "Turn on HTML" as the text/plain part.
Next, people tend to make poor choices when given the chance to decorate text. While I can't kill CAPS LOCK or loads of exclamation points, I can squelch the heavy use of Comic Sans 36.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko