I use the latest version.
The solution obviates the need for infrastructure. The model is pay-per-use. We are not talking about a single email but a complete collaboration suite. One gets very well integrated IT which is tightly stitched with collaborations. One can chat and field calls. As such, it is not only Exchange Online coming on, but Office 365 Suites, which Microsoft provides the users. This availability ranges from first-line workers to CEO level users, depending on one's requirements. All the industry needs are covered. One can take the model best suited to him and tailor his solution to his investment capacity needs.
This means that the solution offers complete scalability and flexibility. A business user who occupies a very small portion of the industry can pay less for a suite. The desktop and web versions are also options. The solution's handy. One can use it on his mobile, or any other devices, including multiple devices and single identity. So, the picture is comprised of many components.