stream {
    upstream imaps {
        server {{ loadbalancer_ip }}:993;
    }
    upstream smtps {
        server {{ loadbalancer_ip }}:465;
    }
    upstream smtptls {
        server {{ loadbalancer_ip }}:587;
    }
    upstream smtp {
        server {{ loadbalancer_ip }}:25;
    }
    upstream managesieve {
        server {{ loadbalancer_ip }}:4190;
    }

    server {
        listen     993;
        proxy_pass imaps;
    }
    server {
        listen     25;
        proxy_pass smtp;
    }
    server {
        listen     587;
        proxy_pass smtptls;
    }
    server {
        listen     465;
        proxy_pass smtps;
    }
    server {
        listen     4190;
        proxy_pass managesieve;
    }
}