Version:           1.9 (using KDE KDE 3.5.0)
Installed from:    Gentoo Packages
Compiler:          gcc 3.3.6 
OS:                Linux

Under a very specific and strange set of circumstances, KMail is creating lots and lots of copies of new messages.  I'm also not entirely sure if this is KMail's fault or Bogofilter's, as you'll see below.  It sounds very similar to bug #38175, however, I've only had it happen in version 1.9.  Here's the list of conditions:

* First off, it's only copying the newest message, even if that message has been read.  It's also only happening with messages that are addressed to multiple recipients.

* A copy is made every time KMail checks for new messages.  I left it running overnight with interval checking turned on and came back to find hundreds of copies of one message!  Actually, KMail couldn't handle opening my inbox with that many messages in there but I was able to see and delete them in Thunderbird and also the webmail interface we've got.

* I have two email accounts set up and the bug only seems to happen when I press the check mail button to check both accounts. (Except for interval checking, that is. I have both accounts set to check every minute so I guess that means they probably get checked at the same time?)  When I hit F5 to refresh just one, it doesn't happen.

* This is only happening for one of my email accounts!  It doesn't happen when I'm using Thunderbird so I don't think there's anything wrong with the server itself.  Perhaps the servers are slightly different and KMail isn't talking quite right to one of them?  I'm told that the problem server is running Postfix and Mailscanner and using UW IMAP.  The one that's not having the problem is using Courier IMAP.

* I tried using Bogofilter to filter out spam in the version of KMail that was with KDE 3.4.3 before I found out that filtering IMAP messages wasn't supported.  I believe it's supported in the new version, right?  Anyway, I don't think this was happening when I had Bogofilter attempting to run before, but in the current version the bug is only occuring when I've got Bogofilter turned on and filtering incoming messages.  I have other basic filters running on incoming messages without any problem.