How can I specifically test raw HTTPS connectivity to `api.segment.io` from my server to isolate the issue from my application code?

You can test raw HTTPS connectivity from your server using `curl` or `openssl s_client`. Execute `curl -v https://api.segment.io/v1/health` to see verbose connection details, including SSL handshake information. Alternatively, `openssl s_client -connect api.segment.io:443` attempts an SSL handshake and displays certificate details. A successful connection will show certificate information; if it fails, the problem lies at a lower level (network, firewall, DNS, or system SSL trust store) independent of your application logic.