- You try to sync a device to a mailbox through Microsoft Exchange ActiveSync (EAS) in a Microsoft Exchange Server 2010 environment.
- The device uses version 12.1 of the EAS protocol or an earlier version of the protocol.
- The device sends EAS requests to a Client Access server that is not located in the Active Directory site in which the Mailbox server resides.
- The Active Directory site in which the Mailbox server is located has a Client Access server that has a published external URL.
For example, you sync an external Android-based device that uses the EAS 12.1 protocol to a mailbox in a different Active Directory site to the Client Access server that responds the EAS requests. However, the synchronization process fails.