In brief: An outage in Microsoft’s Exchange Online transport pipeline (incident EX1331830) caused multi-hour email delays and delivery failures in North America, Europe, and Asia-Pacific.
On June 2, 2026, massive disruptions struck Microsoft’s Exchange Online infrastructure, causing global email delays and connectivity failures. The outage, registered as incident EX1331830, initially affected North America and Germany, later expanding to Europe and the Asia-Pacific region.
The disruption occurred on June 2, 2026 at 10:33 a.m. EDT and manifested itself through errors in the central transport pipeline for email traffic. Affected users received specific error messages: some experienced SMTP rejections with the message “The maximum number of concurrent connections per resource forest has been exceeded, transmission channel is being closed,” while others saw the error message “Connection was abruptly closed (SuspiciousRemoteServerError).” Emails disappeared from the outbox and appeared in sent item folders but failed to reach recipients or arrived with extreme delays.
For CISOs, such an outage presents a significant threat to business continuity. When central communications infrastructure fails, time-critical processes cannot be executed, incident response is hindered, and compliance risks emerge — such as difficulties meeting retention requirements or accessing audit logs. A three-hour outage in Europe and the Asia-Pacific region means massive productivity loss for global organizations and potential regulatory consequences.
Microsoft acknowledged in its status report that “users experienced significant delays sending and receiving email messages,” with “some email messages remaining undelivered for more than one hour.” Telemetry data from external services confirmed a concentration of server degradation in the Germany West Central region, which encompasses the Frankfurt cloud node. At 2:24 p.m. EDT, Microsoft was forced to officially expand the affected regions to Europe and Asia-Pacific.
Microsoft’s incident management team initiated analyses of blocked mail queues and isolated potential sources of error. This was already the next in a series of technical disruptions affecting Microsoft’s cloud services in 2026 — just days earlier, separate incidents had blocked access to Microsoft 365 platforms, including Microsoft Teams and Office on the Web.
Source: www.it-daily.net · Published June 3, 2026
Lumi AI News — AI-assisted curation in accordance with Article 50 EU AI Act. Paraphrase and classification by Lumi News Pipeline v1.2.9.