Exchange behaving now in Beta 5 for me so its worth giving it a go if you have had problems with exchange email accounts in previous betas!
However I yesterday upgraded my exchange 2010 account to exchange 2013 so this might be the cause of mail working better now in Beta 5!
However I yesterday upgraded my exchange 2010 account to exchange 2013 so this might be the cause of mail working better now in Beta 5!