Ok - after a while i installed now the latest i-mscp (1.3.8) and LetsEncrypt (2.0.1)
There must be something in my brain i dont understand or there is something not correct installed.
1. Thunderbird - all certs are made for web4you-server-02.web4you-gmbh.ch see attachement Nr 1.
2. Firefox - this cert is made for web4you-gmbh.ch see attachement Nr.2
3. My postconf looks like attachement Nr. 3.
tnx