Mail conversation view broken on OS X 10.9.4 I upgraded my MacBook (Retina, 15", late 2013) to OS X 10.9.4 yesterday. Now Mail Version 7.3 (1878.6/1878.2) does not display conversations correctly:


As you can see in the screenshot (ignore German localization) in the very right panel, not in the preview, the entire conversation is displayed, but the height of the messages is too small. I can even select all the text in a mail, but I cannot see it or increase the height.
It takes more than one second (!) to display a conversation, no matter how many mails are in it. Used to be instant. Single mails are still displayed instantly.
Sometimes the conversation indicator (e.g. that [2>] in the screenshot is missing even if it actually is and loads a conversation.


Mail is working fine if I disable conversations in the view menu. But I like the converation view and would like to keep it.

Broken output:


Expected output (this is OS X 10.9.3 on my virtual machine):


I tried the following things


no logs in Console.app
I deleted all accounts and all mail settings I could find in my ~/Library/ - no change
I created a new user on my MacBook and entered one of my mail accounts - same problem
switched language to English - no change
compared md5 of /Applications/Mail.app/Contents/MacOS/Mail with other Mail.app's, it still d1911cc8cbdaabc61c409d65b262c5ee - binary not broken
Used my virtual machine with Mac OS X 10.9.3 (everything works fine), replaced /Applications/Mail.app with the version on my 10.9.4 system, still works fine - Mail.app is not causing the problems
compared sizes of /System/Library/Private Frameworks/Mail*.framework - exact same bytecount
I fixed the problem downloading the OS X Mavericks 10.9.4 Update (Combo) from the Apple website and installing it again. Either the App Store version was broken or something went wrong during the installation.