Another popular way of accessing a mailbox is Exchange ActiveSync (EAS). EAS enables devices to synchronize data from your Exchange server mailbox over the air. Typically devices include smart phones and tablets, but regular PC applications have been known to use EAS under the hood as well. A good example of the latter would be the Windows 8 Mail App.

Although Exchange ActiveSync is a stable protocol, its implementation sometimes can be challenging. Every application or mobile OS maker can freely choose what features they will or will not implement. This can lead up to difficult and confusing situations where some devices might work as expected and others don't. Although Microsoft created the ActiveSync logo program in the past to overcome these issues, these problems are still very alive today.