Christian Rößner: Hello Christian,
By changing *_CAfile parameters to *_CApath, everything started working again.
nothing specific to your OpenSSL version but: do you run postfix chroot? from http://www.postfix.org/postconf.5.html#smtpd_tls_CApath:"To use smtpd_tls_CApath in chroot mode, this directory (or a copy) must be inside the chroot jail."
tls_ssl_options = NO_COMPRESSION
as you're using latest postfix+openssl, you may want to add "no_renegotiation"