Upgrade to newer version of Kopano server and Webapp is easy, but i don’t think it will solve your problem.

I don't see where there's any means of upgrading on ClearOS. At least the Devs haven't posted any in the ClearOS repositories, nor are there any forum entries showing how to do that in 2020 or 2021. I would agree it probably wouldn't take care of my issue, which appears to be LDAP related. I think Nick's onto something though.

Check out this thread: https://www.clearos.com/clearfoundation/social/community/update-kopano,-webapp-and-z-push

Be aware that you break the ClearOS updates with this.

I'm currently not using the Kopano updates from COS and following the Kopano repo updates

My versions are currently:
WebApp: 4.6.3.0-155.1
Kopano Core: 8.7.17
Z-Push: 2.6.1+0