After close to 100,000 views and 600 messages on this message board alone, with numerous other links on the right of this page, and nearly 4 1/2 months since Mavericks was released, there has been absolutely nothing officially said nor evidently done by Apple to resolve this issue, if one is to believe the 10.9.1x and 10.9.2 release notes to date. The word 'Exchange' does not appear anywhere.
Mac Mail worked with Exchange. We all installed Mavericks and it stopped working. Nothing else changed. Nothing.
Dozens of different fixes have been described and discussed here and for every one who claims a fix works, another says it doesn't and a third says it only works momentarily.
Why in heaven's name doesn't Apple officially clear the air, write a white paper on configuring Exchange with OS X 10.9 if that is the issue, even just acknowledge the issue exists. They seem to be committed to turning off the whole corporate market. Surely not their marketing strategy.