I don't use this myself but in theory it should work:

  $ apt show claws-mail-fancy-plugin
  Package: claws-mail-fancy-plugin
  Version: 3.14.1-3+b1
  ...

  Description: HTML mail viewer using GTK+2 WebKit
   This plugin for Claws Mail allows rendering of HTML email messages
   in the message window.
   .
   It uses the GTK+2 port of the webkit library to render HTML.
   .
   Supports printing HTML mails when html2ps package is installed.