smtp_use_tls = yes
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
smtp_tls_security_level = may
smtpd_tls_auth_only = yes
smtpd_tls_chain_files =
  /etc/postfix/custom/ssl/server.crts,
  /etc/postfix/ssl/ca.crts
smtpd_tls_key_file = $smtpd_tls_cert_file
smtpd_tls_security_level = may
smtpd_tls_session_cache_database = lmdb:/var/lib/postfix/smtpd_scache
smtpd_tls_session_cache_timeout = 1d