need help reverse-proxy config

[Thierry]

error_log /var/log/nginx/error.log info;

events {
    worker_connections  1024;
}

stream {
    upstream backend {
        hash xxx.xxx.xxx.xxx consistent;

        server email.domain.tld:448;
    }


    server {
        listen 448;
        proxy_connect_timeout 1s;
        proxy_timeout 3s;
        proxy_pass backend;
    }
}

I have difficulties to understand the "main context" idea .... With this 
exemple, is my "stream" in the right context ?? Seems not.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,271891,271899#msg-271899