Troubleshooting Guides commands

• Email not arriving

  MX records, SPF, domain expiry and mail port reachability checked in order with dig, whois and nc.

• Slow or unreachable server

  dig, ping, mtr and nc run in order to tell a DNS, network-path, or application-layer problem apart.

• SSL/TLS certificate errors

  dig, nc and openssl s_client run in order to isolate exactly which part of the TLS setup is actually broken.

• Website is down

  DNS, port, HTTP, and TLS checked in order — dig, nc, curl, openssl s_client — to find exactly which layer failed.