Starting with Kopano Core 8.5 it is no longer possible to directly to upgrade from ZCP 7.1 or earlier, as the database upgrade functionality for old Zarafa versions has been removed. see JIRA tickets KC-859 and KC-839 for more information
From ZCP 7.2 it is still possible to directly upgrade to Kopano Core 8.5 or later.
To upgrade such an installation to Kopano Core 8.5, it is required upgrade to the Kopano Core 188.8.131.52 first, which needs to be downloaded manually.
It is recommended to create a local repository on your system with the install packages to install kopano-server-packages
Afterwards you can switch to the officical Kopano repository and upgrade to the latest Kopano Core release.
Depending on version of your ZCP installation the database upgrade can take some time, take this in account when planning the migration.
Alternatively it is also possible to upgrade to ZCP 7.2 first, but this requires a little more work.
Please contact Kopano Support for more information.
Kopano customers with a valid subscription can get archives with previous releases from https://download.kopano.io/supported/core:/final/tarballs/archives/
If you don't have a Kopano subscription the last (community) Zarafa packages can be downloaded from http://archives.z-hub.io/7.2/