[German]Since Friday, September 5, 2025, users of Exchange Online and Microsoft Teams have noticed that links can no longer be opened. The cause is Microsoft's anti-spam service, which blocks these links for individual users and even moves emails into quarantine. Microsoft is currently working to resolve this issue.
I came across this issue in the following post by my colleagues at Bleeping Computer on BlueSky, which they address in this article.
It is reported that Microsoft is working to resolve a known issue. The anti-spam service is incorrectly preventing Exchange Online and Microsoft Teams users from opening URLs. In addition, some of these users' emails are being quarantined. The message should be MO1148487 – Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams, which Microsoft describes as follows (source).
MO1148487 – Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams
| Status: | serviceDegradation |
|---|---|
| Start Time: | Fri Sep 5 09:10:00 2025 |
| End Time: | N/A |
| Service: | Microsoft 365 suite |
| Feature Group: | Portal |
| Classification: | incident |
| Last Updated: | Mon Sep 8 20:11:10 2025 |
| Root Cause: | An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact. |
| Next Update: | Tuesday, September 9, 2025, at 6:00 PM UTC |
…
| Time: | Next update by: Friday, September 5, 2025, at 10:00 PM UTC |
|---|---|
| Description: | Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams User impact: Users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams. More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user"; however, the URLs are confirmed as safe. Some email messages may also be incorrectly quarantined. Current status: We've identified a new subset of URLs that are impacted and we're working to address the new set and any residual impacted messages. We are confident that a majority of the impact has been resolved, and we're actively addressing lingering impact while we perform our root cause analysis. Scope of impact: Any user receiving email messages or messages within Microsoft Teams containing specific URLs may be affected. Start time: Friday, September 5, 2025, at 1:10 PM UTC Root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact. |
| Time: | Fri Sep 5 14:32:07 2025 |
