Skype for Business (SfB) is a widely used communication tool. When using it with Web Gateway, you must ensure that no HTTPS (SSL) scanning is applied to web traffic going on over this tool.
Web traffic uses default HTTPS ports under Skype for Business, but does not always follow the relevant protocol. If HTTPS scanning is performed on Web Gateway, it detects a mismatch and closes the connection, which leads to a communication break. Audio and video communication can no longer continue using Skype for Business, nor can its desktop sharing feature be used.
Web Gateway is by default configured to detect web traffic using Skype for Business and exempt it from scanning. An option of the SSL Scanner settings is set for this purpose. Be aware, however, that exempting this traffic creates a security risk.