Here comes a quick overview on recent updates to Kolab 16 packages.
Please note: I am only using public information. I have no background knowledge about the releases.
In the past days, the erlang package has been built for Debian Jessie for Plesk, so that version 18.3.4 will be available there. It only affects Debian Jessie packages for Plesk. Guam has been rebuilt due to this.
For details see:
Updated erlang and guam packages for Debian_8.0_Plesk_17 for Kolab 16.1