Kolab intallation on Centos 7

[Gelpi Andrea]

Trying to install Kolab 3.4 on Centos 7 following this docs

https://docs.kolab.org/installation-guide/kolab-3.4/centos-7-community-3.4.html

I got the following errors during yum install kolab.

Installazione : amavisd-new-2.10.1-5.el7.noarch

325/329
warning: group clamupdate does not exist - using root

Installazione : cyrus-imapd-2.5-108.3.el7.kolab_3.4.x86_64

327/329
warning: %post(cyrus-imapd-2.5-108.3.el7.kolab_3.4.x86_64) scriptlet
failed, exit status 1
Non-fatal POSTIN scriptlet failure in rpm package
cyrus-imapd-2.5-108.3.el7.kolab_3.4.x86_64

Installazione : kolab-3.1.9-3.4.el7.kolab_3.4.noarch

329/329
ERROR: Failed to load plugin file
/usr/share/roundcubemail/plugins/zipdownload/zipdownload.phpERROR:
SQLSTATE[HY000] [2002] Can't connect to local MySQL server through
socket '/var/lib/mysql/mysql.sock' (2)Error 500: Error connecting to
database: SQLSTATE[HY000] [2002] Can't connect to local MySQL server
through socket '/var/lib/mysql/mysql.sock' (2)

Are those errors normal?
Have I to correct them in anyway?

ThanYou