As surprising as it sounds, the US Military does not run on a single unified enterprise email solution. Each of the major force components has been running its own email services. Even worse the services don't just vary by branch of service; what's available can vary by command and deployment area.
This has started to change with the Army making the decision to move to the cloud enterprise email solution managed by the Defense Information Systems Agency. The Air Force has also announced that they are planning to make this move, and the DISA is already working with the Navy to make the same change, as reported by Federal News Radio's website.
The Army's project to migrate to the enterprise email system appears to also have been the guinea pig for the other branches of the military. With the goal of migrating almost a million and a half user accounts to the new system, the project, which the Army had scheduled to be completed by this March, seems to have alleviated the concerns of others in the armed services that there would be major problems in making the transition.
Email migration is only the first in a long series of projects to move the DoD into an integrated computing enterprise. The next major project is to move the various SharePoint collaboration servers and their users into the cloud, but there are a large number of smaller independent computing efforts scattered through all parts of the DoD that will not be as obvious as some of the service-wide applications that will be the high-profile projects.
Building an integrated, cloud-based computing enterprise that serves the needs of the military in its various roles seems to have gotten an extra push from the various datacenter closure mandates, but it is a process that is long overdue, with much duplication of effort and experience that could better be applied to building next generation computing infrastructures for the military, rather than the recreating of what other service branches have been doing.