The entries for text/html in /etc/mailcap and ~/.mutt/mailcap on my
~amd64 Gentoo Linux system are

$ grep ^text/html ~/.mutt/mailcap /etc/mailcap
/home/romildo/.mutt/mailcap:text/html; links %s; nametemplate=%s.html; needsterminal; copiousoutput; description=HTMLText
/etc/mailcap:text/html; /usr/bin/lynx -force_html '%s'; needsterminal; description=HTML Text; nametemplate=%s.html
/etc/mailcap:text/html; /usr/bin/lynx -dump -force_html '%s'; copiousoutput; description=HTML Text; nametemplate=%s.html

Although the entry for links does not have the field copiousoutput, it
is not being used for viewing an html attachment from the mutt
attachments menu, as it should be. Instead it is using the lynx entry. I
am using Mutt 1.5.21 (2010-09-15, Gentoo 1.5.21-r1).

Any clues?

Romildo