Mutt

Render HTML email when there's no text/plain alternative

If there's no text/plain version of an email component, mutt defaults to just rendering the html, regardless of the mailcap file.

To make it do something more useful:

.mailcap

text/html; lynx -force_html -dump %s ; copiousoutput

.muttrc

auto_view text/html
alternative_order text/plain

One downside of this, is that lynx no longer can run interactively (you can't follow links from a html email). Instead lynx will print out a references section at the bottom with all the embedded links.