Since I updated to Mavericks two days ago on my late 2008 13-inch MacBook (first unibody aluminium), I have huge difficulties using Mail. When Mail is running, everything slows down extremely (I constantly see beach balls and spend most of the time waiting for any of my inputs showing an effect, not just in Mail but with everything). The activity monitor shows that "Mail" and "com.apple.internetaccounts" both have 90%+ under "% CPU", and most of the time Mail is "Not Responding". The Mail application doesn't show any window during maybe the first hour after trying to open it, and once I see the main window, everything is so slow that even opening an e-mail can - if it works at all - take a loooot of time. Two or three times, I even got a complete freeze, the cursor not moving anymore, the fans (which were running constantly before) shut down; the only thing I could do was holding the power button for five seconds.
I have no firewall app running and have looked into my log file which is available here: http://s000.tinyupload.com/index.php?file_id=55665966095442984994
When I force quit Mail and com.apple.internetaccounts, things run smoothly, so the problem seems to be limited to the Mail application. What might I be able to do to avoid having to force quit Mail and have it respond more smoothly and not hang up?