Microsoft Outlook outage: Microsoft blames backend change, rebalances traffic; service restored after hours

Key points

• On Monday, April 27, 2026, Microsoft confirmed a widespread Outlook.com sign‑in disruption that produced “too many requests” errors and unexpected sign‑outs for many users. Microsoft later said service had recovered after it rebalanced traffic and optimized infrastructure. (bleepingcomputer.com )
• Reports began spiking around 4:50–5:00 a.m. ET and persisted for hours before tapering off late in the day. (windowscentral.com )
• Microsoft initially blamed a “recently introduced” backend change; a rollback did not immediately resolve impact. The company then rebalanced traffic and confirmed normal service after monitoring. (bleepingcomputer.com )
• Some Microsoft posts indicated elevated resource usage in portions of Copilot infrastructure in North America during the incident. (tomsguide.com )

What happened

Outlook.com, Microsoft’s consumer email service that also underpins legacy Hotmail addresses, experienced a service degradation on April 27 that locked many users out of their mailboxes. Affected customers reported repeated prompts, sign‑in loops, and 429 “too many requests” errors. Microsoft acknowledged the outage and labeled it “service degradation,” meaning not all users were impacted simultaneously. (bleepingcomputer.com )

By the evening, Microsoft’s status account said normal service had returned following traffic rebalancing and infrastructure optimization, with additional guidance for users who still needed to take steps on their devices. (tomsguide.com )

Timeline (ET)

• 4:50–5:00 a.m.: Outage reports begin climbing sharply as U.S. workers start their day. (windowscentral.com )
• Morning to afternoon: Microsoft cites a “recently introduced change,” attempts a rollback, then reports the rollback did not give the intended relief; engineers continue investigating rising error rates. (bleepingcomputer.com )
• Afternoon: Microsoft says it has completed a rollback and is monitoring; later notes rebalancing traffic to mitigate. (windowscentral.com )
• Evening: Microsoft posts that the issue has been resolved after rebalancing traffic and optimizing infrastructure; service health “returned to normal.” (tomsguide.com )

How widespread was it?

While Microsoft did not publish user counts, independent outage trackers showed sustained, elevated complaint volumes throughout the business day, with live blogs citing roughly 1,000–1,500 concurrent reports for long stretches before trending downward in the evening. (tomsguide.com )

What Microsoft says was the cause

Microsoft’s early updates pointed to a “recently introduced” backend configuration change and an unexpected increase in error rates across two scenarios. The company later said traffic rebalancing and infrastructure optimization restored service, and separate posts during the day referenced high resource consumption in a portion of Copilot infrastructure in North America. Together, the updates suggest a mix of configuration and capacity factors rather than a security incident. (bleepingcomputer.com )

Who was affected

• Primary impact: Outlook.com (including Hotmail) sign‑in for consumer accounts.
• Secondary friction: Microsoft acknowledged related sign‑in issues the same day affecting Office.com and Microsoft 365 Copilot experiences for some users, though the headline problem centered on Outlook.com access. (bleepingcomputer.com )

If you still can’t sign in

Most users should now be able to access their inboxes. If you’re still stuck, Microsoft guidance and live coverage highlighted these practical steps:

• iPhone/iPad (Apple Mail): Re‑enter your account password under Settings > Mail > Accounts, then reopen Mail to confirm sync. (tomsguide.com )
• Avoid rapid, repeated login attempts that can trigger additional throttling; wait a short period and try again using a single method. (bleepingcomputer.com )
• Check the Microsoft 365 status feed for any residual advisories tied to incident ID CP1293219. (tomsguide.com )

Why it matters

Outlook is a critical personal and business communications backbone. This incident follows a larger Microsoft 365 disruption in January 2026 that affected multiple services, underscoring how configuration and capacity changes can ripple at global scale. (techradar.com )

The bottom line

• April 27’s Outlook.com outage was caused by backend changes and exacerbated by capacity/resource issues; Microsoft ultimately restored service by rebalancing traffic and tuning infrastructure. (bleepingcomputer.com )
• As of late April 27, Microsoft reported service had returned to normal; lingering issues should clear after users complete any device‑specific steps (notably on iOS). (tomsguide.com )