how to re-index Kmail

Riddle me this: new/old problem with Kmail. Ever since I moved to TDE with Debian Jessie, I've had this annoying but minor glitch. When I start up Kmai, I get some message that I need to re-index folders, usually just the inbox, or whatever folder I've used last. Sometimes I see that I have unread emails; these are usually ghosts. (This is a bug that I experienced with the old KDE3, going back to when Noah built the Ark. Anyway, so I just click and mark them read, and I'm done with it until the next time I boot up, when I go through it all again, only with different emails that I need to change from read to unread. Annoying, like I said, but minor, and I was never bothered enough to care. Now when I start up Kmail, I see 39 unread emails, all of which seem to go back to about the same date, apparently sometime in the past week, all of them from the TDE mailing list. They don't go away, not even when I try to mark all the emails in that folder as unread. Only when I download new emails: then the unread emails disappear, but whenever I move anything into the folder (from inbox or sent mail folders), they all reappear once more. And when I start up Kmail again, all those "unread" ghost emails come back; furthermore, the number keeps growing, and they all seem to start from the same date - except that when I search the folder for those emails, there are no unread emails, it's just a number that appears on the Kmail icon in the lower panel. Does anybody else have a problem like this? Or, how do I fix it? Bill