For your CA signed certificates to be trusted, you need to trust your Root certificate or CA if you don't use a Root certificate.

Download the Root 230RO.cer file

Windows

Start > certmgr Right click on Trusted Root Certification Authorities > All Tasks > Import... import import_1 import_2 Browse and select Trusted Root Certification Authorities import_3 import_4

Chrome / Edge

They use the Windows SSL store

Firefox / Thunderbird

Go to Settings and search for Manage certificates firefox firefox_import

Browse and select Root 230RO.cer

Trust this CA to identify web sites Trust this CA to identify email users

firefox_import_1

Linux

Debian

# curl -s https://www.230.ro/en/ssl/Root%20230RO.pem -o /usr/local/share/ca-certificates/Root\ 230RO.crt
# update-ca-certificates
Updating certificates in /etc/ssl/certs...
1 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...
done.

To force the ca-certificates rebuild use update-ca-certificates --fresh