Microsoft’s Outlook.com webmail service has been going through a three-day-long outage that has prevented Australian users from accessing or signing in over the weekend. Users have also reported on Twitter that they couldn’t connect to the email service even before the officially reported start time for the outage (1, 2, 3, 4), with the official Microsoft Outlook account pointing them to the service’s status page for more details. Microsoft has pinpointed the cause of the outage to a Domain Name System (DNS) issue or third-party ISP networking issue.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-outlook-outage-affecting-australians-since-saturday/