Title: Some users may be intermittently unable to send email messages to Outlook.com, Hotmail.com, or Live.com email addresses
User impact: Users may have been unable to send email messages to Outlook.com, Hotmail.com, or Live.com email addresses.
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.
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.
Scope of impact: Some users may have intermittently been unable to send email messages to Outlook, Hotmail, and Live email accounts.
Start time: Friday, November 6, 2026, at 6:00 PM UTC
End time: Monday, November 9, 2026, at 11:02 AM UTC
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.