Mail not encrypted

Dear Admin !
Mail is sent ok but not encrypted.
I try to fix following the web: http://blog-xtraffic.pep.vn/huong-dan-cach-cai-dat-mail-server-voi-postfix-dovecot-cyrus-sasl/
not successful.
Please show me tha way to fix.
Thanks

This will be fixed in next release, meanwhile, you can fix it.

Open

/etc/postfix/main.cf

and append

smtp_tls_security_level = may

and restart postfix

systemctl restart postfix