I use Claws when I need to quickly check an email update or do a simple search, because it's much faster and less memory hungry compared to Thunderbird. In fact, the inability to read HTML emails is pretty much the only thing keeping me from using it as my main mail reader. (I didn't know about this plugin, clunky or otherwise, could you mention that it's called? Also, in what way is it clunky - is it unstable/unreliable, or is it just slow to load or something?)