As for the HTML decoder I might be able to shed some light having probably triggered the UTF-8 support and beta tested the HTML part and having had the odd email chat about this feature with the programmer. Basically there's three kinds of email around: text only, html only and those containing both. The first and third are not problem since the text part will show and usually is no hassle to read well. The drag (or even pain in the a...) is that more and more email is in HTML partially since most Windows apps default to HTML, newsletters prefer that format for enhanced options and SPAM & virusses etc. need the HTML format for automatic action.
The problem with HTML mails is that it is full of HTML tags enclosed in "<" and ">" which make reading hard if you're not using a browser. On the other hand I'm not into using a browser for email reading since it is slow and the risk that the mail contains some image which is loaded from the server and thus confirms my reading the mail validating my address for the sender. Now the new MPro addresses just this issue mainly by removing nearly all HTML tags from HTML only mails (URL references are handled a bit differently) so that the mail is suddenly legible. In addition to displaying the cleased HTML as text the full HTML is presented as attachment.
Overall I must say that this MPro upgrade is one of the best since it really increases usability due to UTF-8 support and HTML stripping. Very good - *thanks* Colin and Andrew.