Microsoft is investigating an Exchange Online outage (initially tracked as EX1189820) that is preventing customers from accessing their mailboxes via the classic Outlook desktop client. First acknowledged at 09:57 AM UTC, the disruption has led to widespread connection and login errors, particularly for users in the Asia Pacific and North America regions. Microsoft has confirmed the issue and is investigating the root cause.

The company stated that it is reviewing service-side logs to determine what is causing the mailbox access issues. These outages follow a series of recent service interruptions across Microsoft 365 and Azure - ranging from major DNS failures to MFA-related login problems and an Azure Front Door CDN incident - each impacting broad user populations across multiple global regions.

These repeated and increasingly interconnected service disruptions have made it critical for organizations to modernize their operational monitoring strategy. Instead of relying on fragmented point solutions that create blind spots, enterprises must adopt a unified, end-to-end infrastructure monitoring platform like NIKSUN that combines full-packet capture with deep packet inspection (DPI), SNMP traps and polling, flow collection, log and event analysis, synthetic transactions, and more. Consolidating these capabilities provides a single authoritative source of truth across NPM, APM, observability, forensics, and availability monitoring. This holistic approach dramatically improves root-cause analysis, reduces mean time to resolution, and strengthens resilience against the complex service-chain failures that now characterize complex environments.