My organization cannot receive external emails.

Thank you for taking the time to send me the above suggestions. My hosting company was able to identify the problem. Apparently, there was malicious content attached to a plugin downloaded.

We have identified the problem and were able to fix it.

All the best.

Hi,

Thank you for the detailed information.

Based on your description, this appears more likely to be related to your domain or DNS configuration rather than the Outlook desktop app or Outlook on the web. Since internal mail flow is working and users can send outbound emails to external recipients, but external senders cannot deliver mail to your organization, the first area I would investigate is the public DNS configuration, particularly the MX record.

Please ask your IT administrator or DNS/domain provider to review the following:

1/ Verify the domain is active with the domain registrar

Even if your Microsoft 365 subscription and billing are current, the domain registration and DNS hosting may be managed separately. Since your website is also inaccessible, please confirm that:

• The domain registration has not expired.
• DNS hosting services are active.
• The configured nameservers are correct and have not been modified unexpectedly.

Navigate to Microsoft 365 Admin Center > Settings > Domains, select the affected domain, and run the Check health or Check DNS option. If any DNS issues are detected, update the records at your DNS provider using the values shown in the portal.

Reference: Having email delivery issues? | Microsoft Learn

2/ Review the MX record configuration

Ensure the domain's MX record points to the correct Microsoft 365 Exchange Online mail endpoint. The MX record tells external mail systems where to deliver messages for your domain. An incorrect, missing, or outdated MX record can prevent inbound email delivery.

Reference: External Domain Name System records for Microsoft 365 - Microsoft 365 Enterprise | Microsoft Learn

4/ Run a Message Trace in the Exchange Admin Center

Ask an external sender to send a test message, then run a Message Trace for the sender and recipient.

• If no trace is found, the message is likely not reaching Microsoft 365, which points to a DNS, MX, domain, or upstream mail-routing issue.
• If the message appears in the trace with a failure, quarantine, or filtering event, the trace details will help identify the cause.

Reference: Message trace in the new EAC in Exchange Online | Microsoft Learn 

5/ Check for any recent DNS, hosting, or nameserver changes

Even if no intentional changes were made, updates at the domain registrar, DNS provider, website host, or third-party email filtering service could affect both website availability and inbound email delivery.

Additionally, please ask an external sender to provide the exact bounce-back or NDR (Non-Delivery Report) message they receive, with any personal information removed. The error code and diagnostic details can help determine whether the issue is related to DNS, MX records, domain registration, mail routing, connectors, or Exchange Online.

If the DNS and MX records are configured correctly but external email still does not reach your Microsoft 365 tenant, I recommend opening a support ticket through the Microsoft 365 Admin Center. Microsoft Support can review the domain status, backend mail flow, and message tracing data in greater detail.

Your IT admin can follow this guide: Get support - Microsoft 365 admin | Microsoft Learn .  

I hope this helps point you in the right direction. Should you have any further questions or need additional assistance, please don't hesitate to reach out. I'm here to help.

Thank you for your patience and cooperation.

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