Summary

On March 18, 2026, a small subset of CodeTwo customers experienced temporary issues with email delivery. The incident was caused by a Microsoft networking and DNS‑related issue within Microsoft 365 infrastructure and was not the result of a failure in the CodeTwo service.

Impact

• Only a limited number of customers were affected.

• The issue occurred intermittently.

• The impact was limited to customers whose mail flow depended on Microsoft 365 services affected by the incident.

Root cause

Microsoft confirmed that the incident (ID MO1255228) was caused by a temporary issue with their networking infrastructure, where part of the infrastructure intended to handle production traffic was only partially reinstated. This led to DNS and load‑balancing issues, affecting services such as Exchange Online.

The incident originated entirely within Microsoft’s infrastructure and was outside of CodeTwo’s control.

Resolution

Microsoft manually reinstated the full networking infrastructure and confirmed service health recovery. Following this action, telemetry indicated stable and healthy service operation.

Why CodeTwo was affected

CodeTwo services integrate directly with Microsoft 365 and Azure and rely on Microsoft‑managed DNS and networking components. DNS failures at the Microsoft platform level affect all services integrated with Microsoft 365, including third‑party solutions.

There is no technically viable way for any Microsoft 365-integrated service to be fully immune to platform‑level DNS or networking failures on Microsoft’s side.

Preventive measures

• CodeTwo services are monitored 24/7/365.

• We operate redundant and failover‑capable infrastructure.

• In case of Microsoft‑side incidents, we take all actions within our control to minimize customer impact, including traffic rerouting where technically possible.

Microsoft stated that this type of incident has been extremely rare and committed to improving safeguards to prevent similar events in the future.

Current status

Microsoft has confirmed that the affected services were fully restored and operating normally. No further issues related to this incident have been observed.