Proxy servers for Teams or Skype for Business Online
This article provides guidance about using a proxy server with Teams or Skype for Business.
Not using a proxy server is recommended
When it comes to Teams or Skype for Business traffic over proxies, Microsoft recommends bypassing proxies. Proxies don't make Teams or Skype for Business more secure because the traffic is already encrypted.
And having a proxy can cause issues. Performance-related problems can be introduced to the environment through latency and packet loss. Issues such as these will result in a negative experience in such Teams or Skype for Business scenarios as audio and video, where real-time streams are essential.
If you need to use a proxy server
Some organizations have no option to bypass a proxy for Teams or Skype for Business traffic. If that's the case for you, the problems mentioned above need to be kept in mind.
Microsoft also strongly recommends:
Using external DNS resolution
Using direct UDP based routing
Allowing UDP traffic
Following the other recommendations in our networking guidelines: Prepare your organization's network for Teams
Following this guidance should minimize potential problems.