DNS is not working

Question

Hello

Please i need your help on this issue.

One of my customer is having an issue where DNS is not working.

We need assistance with their emails working and DNS

Answer 1

Hello, @John Peter,

Welcome to the Microsoft Q&A platform!

DNS issues can disrupt email functionality when records like MX, SPF, DKIM, and DMARC are incorrect, outdated, or misconfigured. Incorrect MX records, for instance, can misguide email routing, while issues such as propagation delays, server outages, or stale cache data can further complicate resolution. Ensuring these records are accurate and current is essential for maintaining reliable email delivery.

To pinpoint the root of the problem, start by verifying your DNS records with tools such as nslookup or online DNS checkers. Check that your MX record and any related A or CNAME records are correctly configured. Additionally, clear the DNS cache on affected systems (using commands like ipconfig /flushdns on Windows) to eliminate issues caused by outdated local cache entries. This process can help determine whether propagation delays or cache problems are affecting email functionality.

Finally, review your email server’s configuration along with the SPF, DKIM, and DMARC records to ensure secure and proper email delivery. Confirm that your DNS servers are operational and consider temporarily switching to reliable public DNS servers—like Google DNS (8.8.8.8 and 8.8.4.4)—to see if resolution improves.

Official Reference Documents:

1.Troubleshooting DNS Servers | Microsoft Learn

2.Find and fix issues after adding your domain or DNS records - Microsoft 365 admin | Microsoft Learn

Should you need more help on this, you can feel free to post back. 

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Thank you for your support and understanding.

Best Wishes,

Alex Zhang

Answer 2

1. Verify the DNS problem exists
   • Can users resolve domain names? (try nslookup example.com or dig example.com)
   • Are only email services affected or all DNS functions?
2. Check basic connectivity
   • Can the customer's network reach DNS servers? (try ping 8.8.8.8)
   • Is this affecting all devices or just some?

Email-Specific DNS Checks

1. MX Record Verification
   • Check if MX records exist and are correct: nslookup -type=mx customerdomain.com
   • Verify priority values are properly set
2. SPF/DKIM/DMARC Records
   • Check for existence and proper configuration of email authentication records
3. A Records for Mail Servers
   • Verify A records for mail servers pointed to by MX records exist and resolve correctly

Common Solutions

1. DNS Server Issues
   • Try switching to public DNS (8.8.8.8, 1.1.1.1) temporarily to test
   • Check if local DNS servers are responding
2. Propagation Problems
   • If DNS changes were recently made, they may not have propagated
   • Check with multiple DNS servers using tools like https://dnschecker.org
3. Firewall/Network Issues
   • Ensure UDP/TCP port 53 isn't blocked
   • Check for DNS filtering or restrictions

Also double check that the domain management service should not be expired with domain hosting provider. Domain service should be in active status.