Directly after the baruwa update I also did a apt-get update && apt-get upgrade. Everything seemed to be working fine. Except after one week around 2:00 AM Mailscanner stopped working. I can see in mail.log that Mailscanner is constantly starting but the queue isn't processed and growing. No mail is delivered.
After a reboot all mails are send and everything is working as expected. Same thing happened to another install after updating (almost after 1 week after updating)