So, since upgrading to Mountain Lion my Exchange email account has stopped working in Mail. For some reason, the OS keeps overwriting the settings to a local mail server from my exchange2010.fasthosts.co.uk account. I've deleted the info in Keychain but Mail appears intent to change the settings. Right now it's broken, any ideas? Thinking of installing another app such as Sparrow but I cannot believe Exchange would be broken under Mountain Lion? Rob.