For all those who don't know I've been using sup to read my office mails.
Sup has a terminal based UI, and like all other terminal based UIs it hates HTML attachments. Even I hate HTML attachments. But some people don't, and they continue to send mails in HTML.
Keying 'enter' on the attachment tells,
'Couldn't execute view command, viewing as text.'
It shows the entire HTML code and, that's ok if you know how to read HTML, but who wants to read html?
So enter pipe.
I press pipe '|' key which invokes the shell pipe on the attachment. Then I type in 'elinks' and press enter.
P.S. : On Fedora, yum install elinks. Elinks is a terminal based web browser. :-)