Version: 1.13.0 (using 4.4.00 (KDE 4.4.0), Kubuntu packages)
OS: Linux (i686) release 2.6.31-20-generic
After upgrading to kmail 4.4.0, sending an e-mail takes nearly one minute after hitting the send button. The composer window stays on screen available for changes for a few seconds and my dual core runs at 70% on both cores. The processes hogging the cpu are nepomukqueryservice, nepomukstorage and virtuoso-t which suggests some weird interaction between kmail and nepomuk. I am available to give you any other information you might need to solve this issue.
After some research it seems that this bug is a duplicate of bug #224037. I'll wait for 4.4.1 to close it if it really is in order.
Actually it is a duplicate of bug 219687, but that one is also fixed in KDE 4.4.1.
*** This bug has been marked as a duplicate of bug 219687 ***