Setting your Exchange Out of Office message through Mail in 10.7
One of the really unknown features that Apple included with Lion is that you can now set your Exchange Out of Office message through Mail.
To configure your Out of Office message, select a folder from the mailbox you wish to set a reply for and click the configuration button at the lower left of the Mail window as shown below. Next, select Out of Office… from the menu which appears. You’ll get the window you see above.