IMAP not working after Renewing the SSL certificates


I needed to renew the SSL Certificate. I followed the steps here

After restart IMAP Login (dovecot) is not working with the following error

 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=, lip=, TLS: SSL_read() failed: error:14094418:SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca: SSL alert number 48,

Seams like dovecot can not find the rootCA. Any hints what I can do to make dovecot and my users happy?
Thanks in advance

Check name and location of the new root certificate and compare it via browser-login with the entries in System - Univention Configuration Registry

On my System with Kopano instead of Dovecot i found the CA in

Did you restart/reload Apache, Postfix and Dovecot after retrieving the new CA?