client ip behind nginx reverse proxy

I'm running an nginx reverse proxy to be able to run multiple servers behind my firewall. I noticed on my (Kerio) mail server the error log is filled with "failed login from < local ip of nginx >" and I was wondering how can I set it so I get the remote IP of the person/bot that is trying to login so I might use that information for auto blocking those addresses (for example)?

This is my current config:

server {
    listen 8443 ssl http2;
    server_name mail.domain.com;

    location / {
        proxy_set_header Host $host;
        proxy_pass https://<internal ip>/;
        client_max_body_size 0;
        proxy_connect_timeout 3600;
        proxy_send_timeout 3600;
        proxy_read_timeout 3600;
        send_timeout 3600;
    }
}

Adding the following lines, results in more of the same:

proxy_set_header   X-Real-IP          $remote_addr;
proxy_set_header   X-Forwarded-For    $proxy_add_x_forwarded_for;

X-Forwarded-For is the feature you need and this will add a http header containing the original client IP. From what you are saying the Kerio Application is ignoring this and just using the Source IP (which is the nginx) in the Logs. Perhaps there is an option to analyse and use this that can be configured on the application.

Just found out my mail server (Kerio) does nothing with the information forwarded by the reverse proxy, so the only thing I can do is hope for an update that does.