Version: 1.13.6 (using KDE 4.6.2) OS: Linux After I upgraded my installation of KDE SC from 4.6.0 to 4.6.2 last monday, Kmail has become extremely slow. This slowness is notable throughout all parts parts of the user interface: When I select an email folder, it takes several seconds (in extreme cases about 10) for the folder contents to be displayed. If the folder has received any new messages since I last had it open, it will again take several seconds for the new messages to appear in the list. When I click on an email in the message list, it takes several seconds for the email to be displayed. When I use the mouse wheel in the message list or the email view, it takes several seconds for it to start scrolling. When I move the mouse over an item in the message or folder view, it takes a few seconds for the item to be highlighted and a tooltip to be displayed. Same goes for the menubar, the icon bar and just about any other widget in Kmails UI. This slowdown did not start gradually, but rather happened quite suddenly after I upgraded from KDE SC 4.6.0 to 4.6.2. Kmail used to be quite snappy before that. No other KDE application (that I use) seems to have been affected by this. Kmail does NOT cause any noticable CPU- or IO-load during this. (Or at least, not more than it always did.) Reproducible: Didn't try Steps to Reproduce: (Example) Open Kmail. Wait for it to poll all configured servers and finish downloading all new messages. Move the mouse cursor over an arbitrary element in the folder list. Actual Results: After more than 5 seconds, the item gets highlighted. Expected Results: The item should be highlighted within significantly less than 1 second. (More like 0.3 seconds maximum) I tried recompiling Kmail after the problems started, but that did not solve te problem. I have several POP3- and IMAP accounts configured. I have several email folders, both local and remote, which contain more than 10000 messages.
Moreover, when I open a received message, I can see a flash of horizontal black stripes before KMail displays the content.
This seems similar to bugs #121347 and #119281. I've had this problem on and off with KDE 4.4.4, but today with 4.6.2 as well. Trying to reproduce this behaviour is a bit difficult, because some days it's okay and others it's impossible to type a mail (I have to resort to an external editor). Considering no other application seems to be affected by this behaviour it must be a bug specific to Kmail.
I just realized that KDE 4.6.* does not have its own kmail package, rather it uses kdepim-4.4.11.1, with kdepim-runtime-4.4.11.1 and kdepimlibs-4.6.2.
Thank you for taking the time to file a bug report. KMail2 was released in 2011, and the entire code base went through significant changes. We are currently in the process of porting to Qt5 and KF5. It is unlikely that these bugs are still valid in KMail2. We welcome you to try out KMail 2 with the KDE 4.14 release and give your feedback.