mail-proxy starttls and ssl on

[bobykus]

The manual 

Setting up SSL/TLS for a Mail Proxy

https://www.nginx.com/resources/admin-guide/mail-proxy/

says  

Enable SSL/TLS for mail proxy with the ssl directive. If the directive is
specified in the mail context, SSL/TLS will be enabled for all mail proxy
servers. You can also enable STLS and STARTTLS with the starttls directive:
mail {
    ...
    ssl      on;
    starttls on;
    ...
}


However if I add both, 


nginx: [warn] "ssl" directive conflicts with "starttls" in
/root/nginx.conf:79
nginx: configuration file /root/nginx.conf test failed

How comes?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,270147,270147#msg-270147