If you need to configure firewall, here are the list of OptiSigns IP addresses and Port to whitelist:
Port: please whitelist HTTPS port 443
- 126.96.36.199 (Files)
- 188.8.131.52 (Files)
- 184.108.40.206 (API)
- 220.127.116.11 (API)
There's no set of IP address for Social Media and some other apps like Google Calendar, so if you really restricting HTTPS access by IP, you may not be able to use those app.