Azure action group not sending emails for outlook contact group
Verify that emails from these three addresses are not blocked:
azure-noreply@microsoft.com
azureemail-noreply@microsoft.com
alerts-noreply@mail.windowsazure.com
It is common that internal mailing lists or distribution lists block emails from external email addresses. You need to whitelist the above email addresses. To test, add a regular work email address (not a mailing list) to the action group and see if alerts arrive to that email.
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/alerts-troubleshoot