When I run Mac Mail it pegs one core to nearly 100%. I bought my MacBook Pro about a year ago and have done every software update. It has behaved this way from the beginning. I connect to my mail server using IMAP. I run Thunderbird, but wanted to use the native Mac Mail. I keep hoping that an upgrade will cure this weird behavior. I've searched the forums, but may not have used the right search terms. Any ideas? Thanks!