Issue accessing auxiliary data through firewall

I’ve been trying to process SLC data using the SNAP toolbox but we are having issues with accessing auxiliary data through our firewall. When the firewall is removed there is no issue, but when it is replaced the auxiliary data is not downloaded. This happens even though the firewall is not blocking . Please could you let me know if there are other websites that the toolbox also needs access to? Although I can work around the precise orbit files, it is an issue for the DEM as this cannot be downloaded separately.

Any help much appreciated