With, I assume, pre-formatted html, as in:
the email is cut off on the right side by the navigation bar on the right, making the quoted email unreadable. I see a lot of sites and especially blogs totally make posts unreadable for this reason.
I guess one answer is to make sure a horizontal scroll bar is available, which I find not UI sane. (scroll-right, scroll-left, scroll-right,scroll-ad nauseam)
I guess, just make the text flow... and have a link to the source.