Resolved after 7 hours 26 minutes, affecting EU Deployment (Other services) and UK Deployment (Other services) and 1 more, on September 4, 2026.
Hello Everyone, **Update:** Incident Resolved. **Date/Time:** September 5th, 16:05 pm UTC Microsoft 365 have advised that the incident is now resolved. NT-ware Operations have also confirmed that the backlog of emails have cleared from the uniFLOW Online mail servers and email delivery to Microsoft 365 based addresses are now back to normal. We are sorry for the inconvenience this has caused. Kind Regards Online Operations Team
Affected components
Update timeline
- investigating Sep 04, 2026, 08:56 AM UTC
Status changed to Investigating
- monitoring Sep 04, 2026, 09:11 AM UTC
**Incident details:** **Start Time:** 4 September 2026, 07:45 am UTC **Incident Scope:** All deployments **Description:** We are currently experiencing problems with delivering email to customers making use of Office 365 with the uniFLOW Online email provider and are investigating. Impacted customers should consider whitelisting the uniFLOW Online email servers although we cannot say if that will resolve the issue, but may help. The IP addresses are documented in the [NT-ware and Online Services DNS / IP addresses](https://ntware.atlassian.net/wiki/spaces/SA/pages/11692015625/NT-ware+and+Online+Services+DNS+IP+addresses#uniFLOW-Online-email-servers) page. **Next Update:** The next update will be in 1 hour.
- investigating Sep 04, 2026, 09:49 AM UTC
**Update:** Currently we can confirm that starting at 07:45 am UTC on 4 September 2026 we have started getting responses back from that we should try again later when attempting to deliver email to customers making use of Office 365 for email. These responses are normally due to greylisting / throttling, but this started around the same time for all our MX's world wide which is unusual. We have also checked with the Office 365 Anti-Spam IP Delist Portal and got confirmation that "The IP address in question is not currently blocked in our system." for our IP addresses. We have also raised a request with Microsoft for further investigation. We are continuing to investigate this issue. **Next Update:** The next update will be in 1 hour.
- identified Sep 04, 2026, 10:59 AM UTC
Status changed to Identified
- monitoring Sep 04, 2026, 10:59 AM UTC
Status changed to Monitoring
- monitoring Sep 04, 2026, 10:59 AM UTC
**Update:** Microsoft has posted EX1467029 in the Microsoft 365 admin center stating that "Users may experience a delay in receiving email messages from external domains in Exchange Online." confirming that this is a Microsoft 365 incident. **Next Update:** There will be no further updates provided for this Microsoft 365 incident. Once Microsoft closes the incident on their side we will proceed to close this incident, alternatively, once we can confirm a return to normal email delivery, we will provide an update and close this incident.
- resolved Sep 04, 2026, 04:23 PM UTC
Status changed to Resolved
- resolved Sep 04, 2026, 04:23 PM UTC
Hello Everyone, **Update:** Incident Resolved. **Date/Time:** September 5th, 16:05 pm UTC Microsoft 365 have advised that the incident is now resolved. NT-ware Operations have also confirmed that the backlog of emails have cleared from the uniFLOW Online mail servers and email delivery to Microsoft 365 based addresses are now back to normal. We are sorry for the inconvenience this has caused. Kind Regards Online Operations Team
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