Updating cache directory
I have gone into the debug log on my work email server while this endless caching process is happening, and I don't see anything that would indicate that there is a problem.
Are you getting errors while installing Windows 10 updates?
My theory right now is that there must be some characteristic of the IMAP server in Kerio Connect that causes Mail to start this endless cache synchronization cycle.
When you download the service pack, it is first placed in a temporary cache location called the Staging Cache.
The following sections describe how to manage the Comm Serve Cache.
I recently ran across a machine that was having problems installing Windows Updates.
Here is an easy fix to Windows Update issues in Windows 10 by clearing the Windows Update cache.
Unless you have manually disabled Windows Update service or used a third-party tool to disable Windows Update, the Windows Update works without any issues for most users.