Add SSL certificate to RedHat/Oracle Linux 7

On Fedora since 19, RHEL / CentOS 7, and RHEL / CentOS 6 since this update, the Shared System Certificates feature is available. With that system, the correct method is to place the certificate to be trusted (in PEM format) in /etc/pki/ca-trust/source/anchors/ and run sudo update-ca-trust. (If the certificate is in OpenSSL’s extended BEGIN TRUSTED CERTIFICATE format, place it in /etc/pki/ca-trust/source).

from here

And for other OS (including Mac OS X): https://manuals.gfi.com/en/kerio/connect/content/server-configuration/ssl-certificates/adding-trusted-root-certificates-to-the-server-1605.html