How to Fix SMTP Error 450 4.4.312 DNS Query Failed in Microsoft 365
Question details
The user needs to resolve an SMTP Error 450 4.4.312 that occurs when Microsoft-hosted senders attempt to email a destination server outside of Microsoft 365.
- Product
- Microsoft 365 / Third-party DNS
- Device & OS
- not provided
- Scenario
- A mail server outside of Microsoft 365 stopped receiving incoming messages from Microsoft-hosted email senders following a recent change in the DNS provider.
- Observed behavior
- Microsoft 365 reports an SMTP error 450 4.4.312 with a DNS ServerFailure response, indicating it cannot successfully query the destination mail server's DNS.
Ensure you have administrative access to your domain's new DNS management console and your mail hosting provider's configuration settings.
Verify and Correct DNS Records with Your Provider
Use this solution to ensure your domain's DNS configurations are correctly mapped to your mail server after a recent provider change.
Because the destination mail server is hosted outside of Microsoft 365, the resolution process relies heavily on the correct configuration of your third-party DNS provider. A recent DNS provider change often causes missing or propagating records.
Navigate to the administrative dashboard of your new DNS hosting provider and open the DNS management or zone editor section.
Check that the MX (Mail Exchanger), A, and PTR records are accurately pointing to your mail server's correct IP addresses.
Review your SPF, DKIM, and DMARC records to ensure they have been migrated properly without syntax errors. Additionally, verify if DNSSEC is configured properly or causing resolution conflicts.
Engage Mail Hosting or Microsoft Support
If standard DNS troubleshooting fails, coordinate with your hosting provider's technical support teams for deeper investigation.
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Frequently Asked Questions
What does SMTP Error 450 4.4.312 DNS Query Failed mean?
This error means the sending email server (in this case, Microsoft 365) experienced a temporary failure when attempting to query the DNS records of the destination email server, preventing the message from being delivered.
Why did this email error start happening after changing my DNS provider?
When you switch DNS providers, necessary records (like MX or A records) might not have been copied over correctly, or the global DNS system is still propagating the changes. If the sending server cannot resolve the new nameservers, it will result in a DNS ServerFailure.
Can Microsoft Support fix my DNS Query Failed error directly?
If your destination mail server is hosted outside of Microsoft 365, Microsoft Support cannot verify or troubleshoot your external configurations. You must work with your external DNS hosting provider first and only contact Microsoft if the provider confirms the issue originates from Microsoft 365.
