Managing e-mail servers is among IT's most painful tasks. It's no wonder, then, that Microsoft chose Exchange as the server product that would capitalize on the benefits of Longhorn first.
The obvious solution for bringing HA (high availability) to your Exchange server is to use Microsoft's own Exchange clustering features. Although Exchange's clustering is reliable and robust, this isn't an easy configuration to set up. It's also usually costly, not only in terms of additional hardware and software licences, but also because it requires a skilled Exchange administrator.
