Microsoft 365 Alert – Service Degradation – Exchange Online – Some users’ legitimate inbound email messages are being marked as spam and quarantined in Exchange Online – RESOLVED

19/05/2023 09:30:00 AM (GMT)

NHSmail Reference : INC35921375

Microsoft Reference : EX556056

Issue Status : RESOLVED

Issue Description : Users’ legitimate inbound email messages are being marked as spam and quarantined in Exchange Online.

More Info : Impact is specific to email messages containing bit.ly URL links.

Final Update : 24/05/2023 09:01:00 AM – After adding a collection of impacted URL domains to Microsoft’s allow list and a majority of affected users have responded that confirming impact remediation. Additionally, monitoring of the issue indicates that users should no longer be experiencing the impact. Please contact your support representative to confirm that your organization is no longer seeing impact or to provide example email messages for review if impact persists.

Scope of impact : Impact is specific to a subset of users receiving email messages containing the affected URL domain via Exchange Online.

Root cause : A logic error in our automated anti-spam algorithm caused it to identify some links to a specific domain within the affected email messages as harmful, leading to impact.