Having a few issues with an Exchange 2010 installation.
Outlook for some users is continually prompting for credentials.
Out of Office Assistant returns: "Your automatic reply settings cannot be displayed because the server is currently unavailable. Try again later."
Outlook runs fine when configured manually however sometimes the Exchange proxy settings change and this breaks Outlook.
This only affects users on 2010/2013, all users on 2003 are fine, so I'm assuming that it's all related to autodiscover.
Browsing to https://Exchange/autodiscover/autodiscover.xml
displays the correct autodiscover page.