Outlook: The host yourdomain could not be found - Socket Error:

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Outlook Error: Socket Error 11001 - Host Not Found

Socket Error 11001 means Outlook cannot resolve the mail server hostname. The server name you entered does not exist in DNS or your computer cannot reach a DNS server to look it up.

Common Causes and Fixes

Typo in the server name: Double-check that your incoming and outgoing server is set to mail.yourdomain.com (using your actual domain name). A single character error will cause this.
Domain DNS not propagated: If you just registered or transferred your domain, the mail DNS record may not be active yet. Wait 24 hours and try again.
No internet connection: Verify you are connected to the internet. Try opening a website in your browser to confirm.
DNS issue on your computer: Try flushing your DNS cache. On Windows: open Command Prompt and run ipconfig /flushdns. On Mac: open Terminal and run sudo dscacheutil -flushcache.
Use the server hostname: If mail.yourdomain.com is not resolving, try using the server hostname from your welcome email as the mail server instead.