On the Appliance, the directory /etc/nginx/conf.d contains two files, the file: grommunio.conf with content:
cat /etc/nginx/conf.d/grommunio.conf
include /usr/share/grommunio-common/nginx.conf;
/usr/share/grommunio-common/nginx.conf includes /usr/share/grommunio-common/nginx/upstreams.d/*.conf;
cat /usr/share/grommunio-common/nginx.conf
include /etc/grommunio-common/nginx/upstreams.d/*.conf;
include /usr/share/grommunio-common/nginx/upstreams.d/*.conf;
error_log /var/log/nginx/nginx-error.log;
access_log /var/log/nginx/nginx-access.log;
...
In /usr/share/grommunio-common/nginx/upstreams.d/ we find the corresponding include files:
ls -l /usr/share/grommunio-common/nginx/upstreams.d/
total 16
-rw-r--r-- 1 root root 75 Aug 3 12:03 grommunio-dav.conf
-rw-r--r-- 1 root root 77 Aug 24 21:02 grommunio-sync.conf
-rw-r--r-- 1 root root 75 Oct 31 16:14 grommunio-web.conf
-rw-r--r-- 1 root root 52 Oct 25 19:00 gromox.conf
This should be the same on Debian - I hope so.