Since KDE 4.6.0, when pressing <delete> after selecting a mail doesn´t move this mail to trash (as it has done <4.6) but asks for a confirmation if I want to move !all! mails of the Mail-Folder the mail is from, to the trash folder. The only way, that I have found, to move a mail to the the trash folder is right-click > move to trash > kmail.folder > trash (or Menu).
I delete (trash) more than 50 mails a day, doing it that way takes more than have of it.

Are you using kmail 1.13.6 or kmail2? I cannot reproduce this bug on opensuse 11.4. I am using kmail 1.13.6 and kde 4.6.1

It is probable you had given focus (if you have focus follows mouse on, this is especially relevant) to the folder list rather than the message list.

i´m using kmail 2.0.89. Not sure when I actually switched to 2.x. So I can´t say if the problem started there.

Are there any kmail specific focus settings? My window focus is on click.

As far as I am aware, there isn't. If you are sure the blue glow surrounds the message view, then please file a bug report at bugs.kde.org.

I can confirm this misbehaviour with kmail 2.0.89!

How to reproduce:
1. Go into a folder with a few mails.
2. select a mail
3. press "del" to move the mail to the trash bin
4. Do step 3 a few times. After a while the selected mail will NOT be moved to the trash bin.
5. To get it working again, I have to click around a bit or restart kmail

I opened a bug report: https://bugs.kde.org/show_bug.cgi?id=270937

Please confirm there if you still have the issue as well.