Hello list,
[server:default]
method = TLSv1.2+
verify_certificate = no
require_certificate = no
private_key = /etc/letsencrypt/live/sbc.example.net-0001/privkey.pem
certificate = /etc/letsencrypt/live/sbc.example.net-0001/fullchain.pem
ca_list = /etc/letsencrypt/live/sbc.example.net-0001/ca_list.pem
#ca_list = /usr/local/etc/kamailio/tls/cacert.pem
#crl = /usr/local/etc/kamailio/tls/crl.pem
server_name = sbc.example.net
server_id = sbc.example.net

#ca_list = /usr/local/etc/fullchain.pem
#ca_list = /usr/local/etc/kamailio/tls/cacert.pem
#crl = /usr/local/etc/kamailio/tls/crl.pem


# ---
# This is the default client domain profile.
# Settings in this domain will be used for all outgoing
# TLS connections that do not match any other
# client domain in this configuration file.
# We require that servers present valid certificate.
#
[client:default]
#method = TLSv1.2+
verify_certificate = yes