Version: (using KDE KDE 3.5.2) Installed from: Ubuntu Packages OS: Linux When one clicks on an hyperlink while reading a mail, KMail first try to see if the document is available (and eventually reply "host not found", etc). Then, the browser (it was Konqueror in my tests) is called. The browser get the page and display it. The problem is that the request to the server is done two times : one by KMail, and one by the browser. If the link is a special URL that only works one time (for example a key as a GET parameter), then you get an error when you actually see the page ("key already used", or things like that).
I think that, like bug 126961, this is something inherent in KDE's URL handling and nothing that can be fixed in Kmail.
This bug has been already reported in http://bugs.kde.org/show_bug.cgi?id=87361 two years ago. I can confirm this bug. For example verifying your email on google will give you a "already verified" as the first request already did its job.
*** This bug has been marked as a duplicate of 87361 ***