I have three Macs (iMac at home, iMac at work and a MacBook Pro Retina 13") and all were upgraded to Mavericks on Tuesday. On the two iMacs, my Exchange (work) accounts -- the inboxes -- aren't updating with new mail or do so very late or only when I shut down and restart Mail. My office is using the latest Exchange Server (Webmail is Outlook-like) and I wasn't having this problem at all under Mountain Lion. All three machines were upgrade from ML. Note the MacBook Pro is working normally. I'm trying to reset Mail on one of the machines and we'll see if that works. Any ideas as to what's wrong? This seems like a major bug.