Hi Folks,
this is my first post. I tried searching for the issue but either found nothing appropriate or took wrong search terms 
The connection from the internet to the Gitlab works just fine:
Internet —> Firewall —> GitLab
The outgoing internet connection is routed via an outbound proxy:
Internet <---- Outgoing Proxy / Firewall <---- Gitlab
I installed and configured the integration for MS Teams.
That works perfectly on a GitLab not connecting through a proxy to the internet.
So MS-Teams site is configured correctly.
On the GitLab connected to the internet via proxy I have timeouts while testing the integration.
There is no blocking rule in the proxy.
When I do the excat same from a Shell using curl, the connection works like a charm.
The systems ENV-variables http_proxy, HTTP_PROXY, https_proxy, HTTPS_PROXY, no_proxy and NO_PROXY are set correctly.
So here is my question:
Is there any place I need to configure the proxy otherwise than the ENV-variables to make the integrations from GitLab to the internet work ?
Or should the GitLab respect the said ENV variables ?
Any hint on where to find the logs for the MS Teams ingetration will also be appreciated. 
If any more info is needed, please let me know.
Greets
Tam