Version: (using KDE KDE 3.5.1) Installed from: Ubuntu Packages In the listing of the parts of an email (attachments, alternatives, etc.) for unknown mime-types "Unknown" is shown in the "Type" column instead of the mime-type found in the value of the Content-Type header of the respective part. The user may have an application to handle the mimetype of the body-part/attachment even if this isn't registered with kde or may want to look for such an application.
If you haven't registered it with KDE, you'll have to save the file to disk, run your application and find the file. Not the best solution. But yes, showing the MIME type should be done, even if "Unknown type (text/x-unknown-found-in-header)"-like. By the way, which types did you receive that KDE didn't know about?
I'm confused: WAITINGFORINFO means "The report does not contain enough information to take any action and requests for more information have so far gone unanswered. If more information appears later, the bug can be reopened." The only question I see in Thiago's comment sounds more like one out of curiosity than an impediment to solve the issue. After all the sentence immediately before the question seems to acknowledge the issue and sketch the solution. But to answer the question: I think at the time the mime type was application/x-turtle, which has in between become official as text/turtle.
Sorry, I probably just missed the question whether this is still an issue in KDE 4.3