Mail.app on Yosemite is murdering my CPU. Every few minutes, mail.app CPU usage jumps to like 158%, stays there for several minutes, then either returns to normal, or I have to force quit the process and restart mail. This has been repeating over and over. I have three mail accounts: iCloud, Gmail, and Exchange, one of each. Did not have this problem on Mavericks. I'm on a 2012 13" MBA i5 8 GB RAM. Anyone else having this issue?