KeyValueExamples
subaccountAny unique identifier of up to 255 characters (regardless of character encoding); Massive will bill requests made from subaccounts separatelyuser@mail.com, user1

Example:

curl -x https://network.joinmassive.com:65535 \
     -U '{PROXY_USERNAME}-subaccount-customer@example.com:{API_KEY}' \
     https://cloudflare.com/cdn-cgi/trace