Queued messages report in the new Exchange admin center in Exchange Online

When messages can't be sent from your organization to your on-premises or partner email servers using connectors, the messages are queued in Microsoft 365. Common examples that cause this condition are:

  • The connector is incorrectly configured.
  • There have been networking or firewall changes in your on-premises environment.

Microsoft 365 will continue to retry to delivery for 24 hours. After 24 hours, the messages will expire and will be returned to the senders in non-delivery reports (also known as a NDRs or bounce messages).

If the queued email volume exceeds the pre-defined threshold (the default value is 200 messages), the information is available in the following locations:

Customize queue alerts

  1. In the Microsoft Defender portal (https://security.microsoft.com), go to Incidents & alerts > Alerts > Alert policy or go directly to https://security.microsoft.com/alertpolicies.

  2. On the Alert policies page, find and select the policy named Messages have been delayed by clicking on the name. You can sort the policies by name or use the Search box.

  3. In the Message have been delayed flyout that appears, you can turn the alert on or off and configure the notification settings.

    Messages have been delayed alert policy details the Microsoft Defender portal.

    • Status: You can toggle the alert on or off.
    • Email recipients and Daily notification limit: Click the Edit link or the Edit policy button to configure the settings as described in the next step.
  4. In the Edit policy flyout that appears, configure the following settings:

    • Send email notifications: The default value is On (selected).
    • Email recipients: The default value is TenantAdmins.
    • Daily notification limit: The default value is No limit.
    • Threshold: The default value is 2000.

    Notification settings in the Messages have been delayed alert policy details.

  5. When you're finished, click Save and Close.


Even if the queued message volume hasn't exceeded the threshold and generated an alert, you can still use the Queued messages report in the new EAC to see messages that have been queued for more than one hour, and take action before the number of queued messages becomes too large.

Queued messages report in the new EAC.

The same information and fix option is displayed after you click View queue in the details of a Messages have been delayed alert.

See also

For more information about other mail flow reports, see Mail flow reports in the new EAC.