Since installing 2.8.6, Apple Mail will no longer sync correctly with my IMAP server. I installed your update on my MacBook Pro and had serious issues with syncing to my IMAP server — it was causing messages to duplicate multiple times and not be deleted from the server when deleted from the Apple client. The Apple Mail client will no longer close correctly.
I was able to replicate on my iMac machine as well. Apple Mail was working fine until I applied the 2.8.6 update. This update has crippled my email!