/etc/postfix/main.cfの設定はこうです｡

# SMTP-AUTH認証
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
smtpd_recipient_restrictions = permit_mynetworks, permit_auth_destination, permit_sasl_authenticated, reject
relayhost = [smtp.ocn.ne.jp]:587
smtp_sasl_password_maps = hash:/etc/postfix/relay_password

# TLS暗号化
#smtpd_use_tls = yes
smtp_tls_security_level = may
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_cert_file = /etc/ssl/private/aaa.crt
smtpd_tls_key_file = /etc/ssl/private/aaa.key
#smtpd_tls_CAfile = /etc/ssl/private/bbb.pem
smtpd_tls_session_cache_database = btree:/etc/postfix/smtpd_scache