The main feature of the coexistence server is to perform Free busy queries between Google Apps, Office 365, and Exchange servers.
This allows the sharing of free/busy information between Google, Office 365, and Exchange servers.
Cloudiway coexistence server is a set of services that enables Google Apps, Office 365, and Exchange to query the calendar availability of each other’s users.
Sharing free/busy data between Google Apps and Office 365 simplifies calendar creation, updates, changes to existing meetings, or recurring meeting series.
Users can query free busy directly from Outlook or from Google calendars.