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Question:

SocketError: WSAHOST_NOT_FOUND No such host is known.

Feb 01 '17 at 09:03

I'm getting this error when trying to send email:

smtpSocketConnect:
socket2Connect:
  connect2:
    connectSocket:
      connect_ipv6_or_ipv4:
        resolveHostname6:
          getAddressInfo:
            Failed to get host address info. (3)
            SocketError: WSAHOST_NOT_FOUND No such host is known.
            hostOrIpAddr: smtp.mail.something.com.au
            port: 25
            Versions of Windows earlier than Windows XP are limited to handling IPv4 only
            On Windows Server 2003 and Windows XP, IPv6 addresses are returned only if IPv6 is installed on the local computer.
          --getAddressInfo
        --resolveHostname6
        Domain to IP address resolution failed.
      --connect_ipv6_or_ipv4
    --connectSocket
    ConnectFailReason: DNS lookup failed
  --connect2
--socket2Connect
Failed to connect to SMTP server..
--smtpSocketConnect

What could be the problem?

---

Answer

This is just a DNS lookup problem. The domain could not be resolved. Either it's not a valid domain name that resolves to an IP address, or the particular system or network has an issue with resolving domains.

For example, open a DOS prompt and type "nslookup amazon.com". You'll see that it resolves to an IP address. Then try the same with problematic domain in the error message. You'll likely see nslookup pause for a short while and then issue an error message.

If "nslookup amazon.com" failed, then it's a system admin problem for that particular computer, or that particular local network, or perhaps some intermittent network issue.

If "nslookup amazon.com" succeeds, but "nslookup smtp.mail.something.com.au" fails, then it's an invalid domain name that does not resolve to any IP address.