Mountain Lion / Mac mail disconnects from MS Exchange server.

We use an MS Exchange account for our company email. We bought 2 new retina display MacBook Pros running Mountain Lion last Fall. My old laptop is still running Lion. Lion / Mac Mail works fine on the old laptop, never losing contact with the MS Exchange server. Mountain Lion / Mac Mail randomly loses contact with our exchange server on a regular basis. This results in a slow and painful re-download of 2 years worth of email while I have to resort to my old laptop to keep up with new incoming email. I check these discussions occasionally when I can find a spare moment and I have found some similar symptoms being complained about, but no solutions yet. There have been a couple of OS updates since we bought the new laptops, but alas, no mention of this problem. It seems no one is doing anything about it. Have I missed a post? Anyone have any suggestions? This is getting really old.

Thanks!
D