Internal server error while adding Event Grid Namespace Custom MQTT Domain

@Stijn Stragier

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The error encountered when re-adding a previously removed custom domain to Azure with a different Key Vault certificate often indicates lingering issues with underlying Azure resources, such as certificate bindings or DNS settings, or it may be a transient backend issue. This error is not uncommon and can be related to internal state mismatches, certificate object persistence, or DNS record conflicts from the earlier configuration. Here are a breakdown and practical steps for resolution:

Why This Error Occurs

• Resource Binding Issues: After removing a domain, some resources or bindings may not be fully cleaned up, especially certificates associated with the previous custom domain setup[.
• DNS or Verification Record Conflicts: DNS records (CNAME, TXT) from the prior domain setup may interfere if not cleared or updated with the new configuration.
• Azure Backend Delays: Azure sometimes requires additional time to propagate changes and release old resource states, causing transient internal server errors when trying to promptly re-add the domain.
• Certificate Reference Conflict: Trying to use a different Key Vault certificate right after removing the previous setup may clash with lingering managed certificate objects.

Immediate Actions

• Wait and Retry: Give Azure more time (from several minutes to a few hours) before retrying the custom domain addition; propagation and cleanup delays usually resolve internal errors between attempts.
• Clear Browser and DNS Cache: Clear your browser cache/cookies and run ipconfig /flushdns on your workstation, as local DNS caching can also cause persistent errors despite successful resource changes on Azure.
• Verify DNS and Certificate Setup: Ensure all required DNS records (CNAME or TXT for domain verification) are correctly pointed and updated for the domain, especially if switching certificates or endpoints. Make sure the Key Vault certificate is active, valid, and properly configured for the domain binding.
• Check Resource State: Inspect the custom domain and certificate objects in Azure Portal for any residual bindings or errors. Delete or update any lingering configurations that could block re-assignment.

Advanced Troubleshooting

• Azure Support Channels: If the error persists after retrying and validating DNS/certificate settings, report the error code and correlation ID (e.g., df847fd6-e65e-42be-b6e9-7b6a58f52f46 from the error message) to Microsoft forums, or submit a support ticket with domain name, resource details, and timestamp for deeper investigation.
• Review Azure Documentation: Reference Microsoft’s troubleshooting guides to cross-check domain and certificate configuration steps, and confirm permissions to modify resources.

Summary Table

If these steps do not resolve the issue and the error persists beyond a reasonable retry window, escalation to Azure support with all error details will be necessary for backend troubleshooting.

you can check below for the reference:

https://learn.microsoft.com/en-us/answers/questions/565321/azure-web-app-custom-domain-problem

https://docs.azure.cn/en-us/app-service/troubleshoot-domain-ssl-certificates

https://learn.microsoft.com/en-us/answers/questions/1513139/error-adding-domain-to-custom-static-web-app

https://learn.microsoft.com/en-us/entra/fundamentals/add-custom-domain

I hope this helps in resolving the issue, do let me know if you have any further questions on this