Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

Title: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

User impact: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

More info: Impact more heavily affects Outlook.com users.

Current status: We’ve confirmed that service availability has almost returned to normal levels, and most users should be experiencing relief. For the remaining limited impact, we’re continuing to perform systematic restarts to ensure full recovery.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A portion of infrastructure responsible for processing request flow traffic is operating below expected thresholds, resulting in impact.

Next update by: Wednesday, October 1, 2025, at 12:30 PM UTC

We’re continuing to observe steady improvements in service availability while the backlog of messages is progressing as expected.

This quick update is designed to give the latest information on this issue.

Title: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

User impact: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

More info: Impact more heavily affects Outlook.com users.

Current status: Service availability is steadily improving, and the backlog of messages is being processed. We’re actively monitoring service telemetry to ensure a complete recovery.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A portion of infrastructure responsible for processing request flow traffic is operating below expected thresholds, resulting in impact.

Next update by: Wednesday, October 1, 2025, at 10:30 AM UTC

We’re observing improvements in service availability following our targeted restarts. We’re closely monitoring to ensure full recovery.

This quick update is designed to give the latest information on this issue.

We’re continuing to closely monitor service availability and we're performing additional targeted restarts where required.

This quick update is designed to give the latest information on this issue.

Title: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

User impact: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

More info: Impact more heavily affects Outlook.com users.

Current status: We’ve confirmed the revert and subsequent manual restarts of affected infrastructure has been successful. We’ll continue to apply these targeted restarts as we monitor the service for recovery.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A portion of infrastructure responsible for processing request flow traffic that isn't operating at expected thresholds and this is resulting in impact.

Next update by: Wednesday, October 1, 2025, at 8:30 AM UTC

As we monitor the service revert, we’re also applying smaller targeted reboots of affected infrastructure to further alleviate impact. We’re slowly seeing a gradual decrease in traffic errors.

This quick update is designed to give the latest information on this issue.

Title: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

User impact: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

More info: Impact more heavily affects Outlook.com users.

Current status: We’ve isolated and have reverted a recent configuration change that we suspect to be contributing to user impact. We'll continue monitoring this revert and in tandem we'll explore additional solutions to further expedite mitigation efforts.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A portion of infrastructure responsible for processing request flow traffic that isn't operating at expected thresholds, and this is resulting in impact.

Next update by: Wednesday, October 1, 2025, at 7:00 AM UTC

Title: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

User impact: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

More info: Impact more heavily affects Outlook.com users.

Current status: We're continuing to monitor our traffic redistribution out of the affected infrastructure, however this is not resolving the impact as we anticipated. We’re reviewing additional logging to develop alternate mitigation options to address the continual service errors.

In addition, we've confirmed impact is more heavily affecting Outlook.com users rather than our Microsoft 365 Exchange users.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A portion of infrastructure responsible for processing request flow traffic that isn't operating at expected thresholds and this is resulting in impact.

Next update by: Wednesday, October 1, 2025, at 6:00 AM UTC

Title: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods

User impact: Users may experience errors or failures when accessing their mailbox in one or more Exchange Online connection methods.

Current status: We've identified a portion of infrastructure responsible for processing request flow traffic that isn't operating at expected thresholds. We've since redistributed traffic to alternate infrastructure and are monitoring to confirm if our actions alleviate impact as expected.

Scope of impact: Users attempting to access their mailbox in one or more Exchange Online connection methods may be impacted.

Root cause: A portion of infrastructure responsible for processing request flow traffic that isn't operating at expected thresholds and this is resulting in impact.

Next update by: Wednesday, October 1, 2025, at 4:00 AM UTC

Title: Potential issues accessing mailboxes via one or more connection methods

User impact: Users may experience errors or failures when accessing their mailbox via one or more Exchange Online connection methods.

Current status: We're investigating a potential issue and checking for impact to your organization. We'll provide an update within 60 minutes.