I am using nginx to issue redirects for a domain we are changing, but one of our old mobile apps becomes broken by this redirect when it issues one specific POST request to the old domain.

Here is the current nginx configuration, how could I add a reverse proxy to perform a POST to the URL /post_url and redirect everything else the same as now?

server {
      listen 80;
      server_name olddomain.com www.olddomain.com;
      rewrite ^(.*) http://www.newdomain.com$1 permanent;
}