Exchange 2007 Leap year bug
When trying to make certain configuration changes such as new-mailbox or enable-mailbox, certain set of our customers would receive the following error:
"The Exchange server address list service failed to respond. This could be because of an address list or email address policy configuration error."
If you are experiencing these symptoms, please read an important post at the You Had Me At EHLO blog: Exchange Server 2007 and leap year day Feb 29 2008...
That is probably a bug in Exchange Server 2007 that Microsoft is trying to resolve.