We want to setup a Bitbucket connection to a server which is not in our network and thus needs to run over our proxy. We have the proxy server configured in the manage Jenkins -> Plugins -> Advance Tab, but the connection to the Bitbucket still fails. We can access the Bitbucket through the webbrowser and via terminal just fine, so it's not an issue of our proxy or firewall related, it must be something jenkins does.

Please find attached the error the proxy page displays.

We use Jenkins 2.356 hosted on Ubuntu 16.04