It's not a bug, just a missing feature. The programmer that created that feature never implemented that behavior due to technical difficulties. We do not consider it as a top priority either, because it has quite few interest to see the number of mails diminish exactly at the moment you change a mail status.
So, I mark this feature request as wishlist and we'll see if we have time to do it, but I can't promise you anything.
It's not a bug, just a missing feature. The programmer that created that feature never implemented that behavior due to technical difficulties. We do not consider it as a top priority either, because it has quite few interest to see the number of mails diminish exactly at the moment you change a mail status.
So, I mark this feature request as wishlist and we'll see if we have time to do it, but I can't promise you anything.