How to reproduce:
 * Get a mail with an attachment named Q
 * Right click on the attachment and choose save as
 * Go to a folder where you have a file named Q
 * Press Save
 * Get a dialog "there's already a file named Q"
 * Now you're going to loose your file named Q
 * Press "rename"
 * The file you had named Q is overwritten

It could be fixed by doing this

diff --git a/messageviewer/utils/util.cpp b/messageviewer/utils/util.cpp
index 18717d4..c0448e6 100644
--- a/messageviewer/utils/util.cpp
+++ b/messageviewer/utils/util.cpp
@@ -272,7 +272,7 @@ bool Util::saveContents( QWidget *parent, const QList<KMime::Content*> &contents
       if( !(result == PimCommon::RenameFileDialog::RENAMEFILE_OVERWRITEALL ||
               result == PimCommon::RenameFileDialog::RENAMEFILE_IGNOREALL ))
       {
-          if ( KIO::NetAccess::exists( curUrl, KIO::NetAccess::DestinationSide, parent ) ) {
+          while ( KIO::NetAccess::exists( curUrl, KIO::NetAccess::DestinationSide, parent ) ) {
               if ( contents.count() == 1 ) {
                   PimCommon::RenameFileDialog *dlg = new PimCommon::RenameFileDialog(curUrl,false, parent);
                   result = static_cast<PimCommon::RenameFileDialog::RenameFileDialogResult>(dlg->exec());


But probably should be fixed inside RenameFileDialog itself since there are more users like kaddressbook/ that also seem to assume that the file they get out of RenameFileDialog is good to go.