WinMail Opener

Does Winmail opener already qualify as a portable app? It can be found on this page:
http://www.eolsoft.com/download/

Winmail Opener is designed to open the notorious winmail.dat files from Outlook Express users, and it can save the text in rtf format. It also has a pane for attachments, if there were any in the message. The installer file is only 299KB.

I can't access (i.e., don't dare to touch on pain of death and dismemberment, or at least on pain of recrimination and disciplinary action) the registry on my employer's computer so can't tell whether it puts anything there. The installer file seems to have just extracted everything to a folder on my USB and I don't see anything in Program Files... so by outward signs it looks as though it's self-contained.

But if it isn't, I'd be grateful for a truly portable version!