Exchange Connection Problems

Fix Microsoft 365 MX Record Has No A Record Issue

Kushani Nimanthika Oct 23, 2026 869 views

Question details

The user needs to resolve an issue where mail flow fails after adding a custom domain to Microsoft 365 because the MX record appears to lack an associated A record.

How to Fix Microsoft 365 MX Record Has No A Record

Product: Microsoft 365 Exchange
Device & OS: not provided
Scenario: Configuring custom domain DNS records for Microsoft 365 to enable proper mail delivery.
Observed behavior: Mail delivery fails and domain configuration warnings appear, leading the user to suspect that a separate A record is required for the MX hostname at their DNS provider.

Before you start

Ensure you have administrator access to both your Microsoft 365 Admin Center and your domain registrar's DNS management console.

Solution 1Recommended

Verify and Update Microsoft 365 DNS Records

Manually copy the exact MX, TXT, and CNAME records provided by Microsoft into your domain provider's DNS settings and verify the domain health.

An MX hostname provided by Microsoft does not necessarily require you to manually create a separate A record at your DNS provider. Microsoft manages the underlying A records for their Exchange mail servers.

To fix mail flow issues, you must ensure that your custom domain uses the exact DNS values specified in the Microsoft 365 portal without any typos or unauthorized modifications.

Access the Microsoft 365 Admin Center

Log in to the Microsoft 365 Admin Center, navigate to 'Settings', and then select 'Domains'. Choose the custom domain you are trying to configure.

Locate Required DNS Records

Click on 'DNS records' or 'Continue setup' to view the exact MX, TXT, and CNAME record values that Microsoft requires for your domain.

Update Your Domain Provider Settings

Open a new tab and log in to your domain provider's portal (e.g., GoDaddy, Namecheap). Navigate to the DNS management page and add or replace your existing MX records with the ones copied from Microsoft 365.

Check Domain Health

Return to the Microsoft 365 Admin Center and click 'Check health' on the Domains page. Wait for the status to show as 'Healthy'.

Verify and Update Microsoft 365 DNS Records

DNS Propagation Time: DNS changes may take anywhere from 30 minutes to 48 hours to fully propagate across the internet. Mail flow will resume once propagation is complete.

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Frequently Asked Questions

Do I need to manually create an A record for my Microsoft 365 MX record?

No. The MX hostname supplied by Microsoft points to Microsoft's own servers. Microsoft manages the necessary A records on their end, so you only need to ensure the MX record itself is correctly added to your domain registrar.

Why is my mail still failing even though my Microsoft 365 domain status is healthy?

If your domain shows as 'Healthy' but mail flow is still failing, DNS propagation might still be occurring globally. Wait up to 48 hours. If the problem persists, you should contact Microsoft Support or your domain registrar for further investigation.

What other DNS records are required besides the MX record?

Alongside the MX record (which handles incoming mail), you must also add the TXT record (for SPF, which helps prevent your emails from being marked as spam) and CNAME records (which handle Autodiscover for setting up mail clients).

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