Microsoft has announced that the 50,000-59,999 port range (UDP and TCP) no longer is a requirement for Skype for Business endpoints to communicate with Skype for Business Online.
Earlier this year Microsoft talked about making simplification for network connectivity for Skype for Business Online (see blog article) and they recently updated the guidance and removed the mentioned port range as a requirement: Office 365 URLs and IP address ranges
**So which ports are required for clients?**All clients need to be able to directly connect to Skype for Business Online on the following destination ports: (the IP addresses and FQDNs can be found in the Office 365 URLs and IP address ranges)
- TCP 443
- UDP 3478, 3479, 3480, 3481
- Optional: UDP/TCP 50,000-59,999
Is there a minimum client version required to benefit from the port changes?
This change applies to all clients supported against Skype for Business Online. No clients are excluded and there are no specific minimum version required (although it is always recommended to run the latest and greatest version).