Zix - Microsoft 365 - Unable to send/receive

Update timeline

1. investigating Jan 22, 2026, 07:59 PM UTC

   We are getting multiple reports of M365 users unable to send or receive emails. Microsoft has posted a couple of Service Alerts due to the volume of reports. At this time, the server alerts are providing general information. We will post an update as soon as they provide more details. Microsoft Service Alerts: Issue ID - MO1221364 As Microsoft rapidly pursue an investigation into the nature of the impact and the source of the issue, Microsoft received reports that users may be receiving a "451 4.3.2 temporary server issue" error message when attempting to access the service portals or use Outlook Issue ID - EX1221363 Microsoft is investigating a potential issue and checking for impact to your organization. Users may experience errors or failures when accessing their mailbox via one or more Exchange Online connection methods.

2. investigating Jan 22, 2026, 08:05 PM UTC

   Update from Microsoft: Issue ID - MO1221364 Some of the impacted service functions include, but may not be limited to: - Sending and receiving email through Exchange Online - Accessing service portals

3. identified Jan 22, 2026, 08:44 PM UTC

   Update from Microsoft: Issue ID - MO1221364 Microsoft identified a portion of dependent service infrastructure in the North America region that is not processing traffic as expected. This is impacting Microsoft load balancing processes and general service availability. Microsoft is working to restore this infrastructure to a heathy state and rebalance the service traffic to achieve recovery.

4. identified Jan 22, 2026, 09:18 PM UTC

   Update from Microsoft: Issue ID - MO1221364 Current status: While Microsoft restored the affected infrastructure to a heathy state, further load balancing is required to mitigate persistent impact. Microsoft identified and are implementing additional actions to direct requests and traffic to additional healthy sections of infrastructure to achieve withstanding recovery.

5. identified Jan 22, 2026, 10:11 PM UTC

   Issue ID - MO1221364 Microsoft has implemented a traffic balancing solution within a limited portion of infrastructure and telemetry shows success. Microsoft is applying this solution incrementally across all affected infrastructure to ensure the environment remains balanced as recovery continues. This quick update is designed to give the latest information on this issue.

6. identified Jan 22, 2026, 11:19 PM UTC

   Update from Microsoft: Issue ID - MO1221364 Current status: Microsoft is carefully rebalancing traffic across all affected infrastructure in the region, while monitoring the corresponding health telemetry, to ensure the environment enters into a balanced state as their remediation efforts continue. Microsoft is proceeding as quickly as possible and this incremental approach will also help them identify whether any additional actions may be required to ensure longstanding recovery.

7. identified Jan 23, 2026, 01:50 AM UTC

   Update from Microsoft: Issue ID - MO1221364 Current status: Microsoft is continuing to refine their load balancing configurations to remedy residual imbalances across the environment and further their ongoing recovery efforts.

8. monitoring Jan 23, 2026, 02:57 AM UTC

   Update from Microsoft: Issue ID - MO1221364 Microsoft is seeing continued improvements in service availability and functionality as a result of our load-balancing efforts. Microsoft is actively monitoring performance and making targeted adjustments to further improve stability and availability, while continuing recovery actions to ensure a reliable service experience.

9. resolved Jan 23, 2026, 01:01 PM UTC

   Update from Microsoft: Microsoft confirmed that the affected infrastructure has returned to a healthy state and is operating as expected. Microsoft will continue to closely monitor the remediation actions taken and make any necessary adjustments to maintain stability. If users experience any residual issues, clearing local DNS caches or temporarily lowering DNS TTL values may help ensure a quicker remediation.