We have been facing some connectivity issues in establishing the connection with the DocuSign API services for a sandbox account. The firewall within the network from which we are trying to access the services is blocking the outgoing requests. To open the ports in the firewall we would like to know the static IP address and ports of the sandbox account. https://demo.docusign.net/api/3.0
See https://www.docusign.com/trust/security/esignature for the current list.
Note that the list is updated frequently, so you will need to track it.