Live status of all services Incident · resolved

Some users may be intermittently unable to send email messages to Outlook.com, Hotmail.com, or Live.com email addresses

Exchange Online EX1545193

Users may have been unable to send email messages to Outlook.com, Hotmail.com, or Live.com email addresses.

Status
Service restored
Feature
Mailflow - delayed sending to Internet
Region
Not specified (all regions)
Started
Nov 6, 2026, 19:00 CET
Resolved
Nov 9, 2026, 12:02 CET
Duration
2 days 17 h

More info

Users may have received a Non-Delivery Report (NDR) reporting 550 5.7.1 or 550 5.7.23 due to Service Provider Foundation (SPF) violation.

Scope of impact

Some users may have intermittently been unable to send email messages to Outlook, Hotmail, and Live email accounts.

Root cause

A recent update to the spam enforcement rules caused email messages to be incorrectly marked and blocked, which led to impact.

Next steps:
- We're reviewing our update procedures and improving our mail detection logic to lower the false positive rate and ensure that legitimate email messages aren’t inaccurately blocked.

This is the final update for the event.

Final status

We've investigated the provided logs and our service health telemetry, and identified a recent update to the spam enforcement rules caused email messages to be incorrectly marked and blocked, which led to impact. We've fully rolled back this update and confirmed that mail flow has been restored and impact is resolved.

Timeline

Every update Microsoft posted for this issue, newest first.

  1. Nov 10, 2026, 06:36 CET

    We've investigated the provided logs and our service health telemetry, and identified a recent update to the spam enforcement rules caused email messages to be incorrectly marked and blocked, which led to impact. We've fully rolled back this update and confirmed that mail flow has been restored and impact is resolved.

  2. Nov 9, 2026, 06:24 CET

    We've received reports indicating that some users may be unable to send email messages to Outlook.com, Hotmail.com or Live.com email addresses. We're requesting that affected users reach out to their support representatives and provide fresh Network Message IDs, fresh logs, and examples of impact users are facing in .eml format. These logs will aid in the root cause investigation into why impact persists, so we can identify a remediation plan.

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Source: Microsoft Graph, Service Communications API. This is the view of a Swiss Microsoft 365 tenant: services not licensed there are missing, and individual issues may affect your tenant differently. Microsoft names the region only in the issue text. The Switzerland view shows issues for Switzerland, for Europe in general and those without a region, but not issues that only name other countries such as Germany or the UK. This page is not provided by Microsoft.