Unexpected Exchange mailbox Server error: Server: [server01.XXXX.XX] User: [[email protected]] HTTP status code: [503]. Verify that the Exchange mailbox Server is working correctly.

If you got this error, please follow this steps:

1. Try disabling the firewall
2. Reset Exchange Folder in IIS – http://support.microsoft.com/kb/883380 (Dont remove exchange-oma)
3. Remove Exchange-oma and create it again http://support.microsoft.com/kb/817379
4. Remove IPV6 from the server