need help reverse-proxy config

[Thierry]

Dear,

I  have a reverse-proxy in front of my two servers: web (apache2) and 
email (nginx-iredmail).
The  proxy-reverse  is  perfectly working with my web server running  
Apache2, but I am not able to make it working for my email server.
The  reverse-proxy and the email server are both running with the same 
version of Nginx (1.9).

I have tried many configs without any success.
My last one:

***********************************************************************

  server {
        listen 446;
        server_name email.domain.ltd;

location / {
        proxy_pass https://email_server_ip:446;

        proxy_ssl_certificate        /etc/ssl/certs/cert.chained.crt;
        proxy_ssl_certificate_key    /etc/ssl/private/private.key;
        proxy_ssl_protocols           TLSv1 TLSv1.1 TLSv1.2;
        proxy_ssl_ciphers             HIGH:!aNULL:!MD5;
        proxy_ssl_trusted_certificate /etc/ssl/certs/cert.chained.crt;

        proxy_ssl_verify        on;
        proxy_ssl_verify_depth  2;
        proxy_ssl_session_reuse on;
        error_log /var/log/nginx/error-proxy.log;
        access_log /var/log/nginx/access-proxy.log;
    }
}

Can I please have some help ??
Thx
  

-- 
Cordialement,
 Thierry                          e-mail : lenaigst at maelenn.org  
 PGP Key: 0xB7E3B9CD