A server-to-server migration method to take Zimbra calendar and contacts and migrate them into Microsoft Office 365. If you can migrate your email from Zimbra into Office 365 it's only a little more effort to move your calendars as well. The application works by using the REST protocol on Zimbra and mapping the corresponding user to Office 365 via an administrator-defined list. This is usually the same list you use for migrating email. The application uses the Microsoft Graph API on Office 365 to insert calendar data for the defined users.
||Free to try
Windows Server 2008
||Zimbra 8.x, Windows, Office 365