docker-machine behind corporate proxy

As previously mentioned, you can edit the file at

$HOME\.docker\machine\machines\default\config.json

and set the HTTP_PROXY, HTTPS_PROXY and NO_PROXY variables (or delete them):

 "HostOptions": {
        "Driver": "",
        ...
        "EngineOptions": {
           ...
            "Env": [
              "HTTP_PROXY=http://10.121.8.110:8080",
              "HTTPS_PROXY=http://10.121.8.110:8080",
              "NO_PROXY=192.168.23.4"
            ],

After the file has edited, you only have to execute:

docker-machine provision