Hi,
I use a mime-hook like this for inline html:
in ~/.sup/hooks$ cat mime-decode.rb :

 case content_type
 when "text/html"
   `/usr/bin/lynx -dump '#{filename}'`
 end

To view html when hitting enter you could set your browser in ~/.mailcap:

 text/html; firefox %s

best,
/p

Excerpts from Steve's message of Wed May 11 14:53:27 +0100 2011:
> Hi,
> 
> A couple days ago, a significant portion of my incoming mail is
> arriving as an HTML attachment only, where previously, HTML formatted
> emails showed up as semi-readable text and also as an attachment.  I
> have not messed with sup recently.
> 
> How do you recommend dealing with HTML attachments?  I hit <enter> on
> the attachment and it says "Couldn't execute view command, viewing as
> text."  Any way to bring this up in a web browser?
> 
> Thanks.