Microsoft 365 outage hits Outlook and Teams users across the UK

What happened

According to AOL UK's live coverage, Downdetector first showed a spike in UK reports of Microsoft Teams problems at around 6.15pm on Thursday 12 November. Problems were still being reported at 3am and into Friday 13 November, when people trying to use Teams and Outlook could not connect.

We felt it at Sayu too. Our colleague Ryan Lee posted this in our team chat at 7.39am on Friday:

Outlook reports on Downdetector peaked at around 140,000 and later dropped to around 28,000. Downdetector heat maps suggested London was one of the hardest-hit areas. These figures count the people who chose to report a problem, so they show the scale of complaints rather than an exact number of affected users. In the US and Canada, Downdetector logged roughly 129,000 to 150,000 Outlook problem reports on Thursday.

Microsoft listed these affected services:

• Exchange Online (Outlook email)
• Microsoft Teams
• SharePoint Online
• Microsoft 365 Copilot
• Microsoft Defender XDR
• Microsoft Planner
• Microsoft To Do
• Microsoft Intune
• Microsoft Defender for Office 365

The impact reached well beyond offices. Canadian hospitals and universities were affected, and Via Rail warned passengers they might not receive trip emails.

What Microsoft has said, and what is still uncertain

Microsoft said the problem came from extra load on its infrastructure, caused by a number of servers being unexpectedly unavailable. A process on those servers that sets up secure connections became overwhelmed. Microsoft linked the start of the impact to a recent network configuration change, which it was reverting. It also applied temporary traffic limits in some locations.

Microsoft said the outage was unrelated to any cyber attack. A senior Microsoft executive, Charles Lamanna, said there was no indication of malicious or cyber activity.

Overnight, Microsoft reported good results from restarting affected servers and partial recovery across regions. It said that recovery had not held. As of early Friday morning UK time, the outage was ongoing and Microsoft was running several workstreams to restore service. Later on Friday morning, Microsoft said it was seeing "encouraging recovery progress, with service availability and email delivery performance improving across a growing portion of affected Microsoft 365 infrastructure". It had not yet said the outage was fully fixed, and Downdetector was still showing tens of thousands of problem reports.

What we do not yet know is when service will be fully back and whether any emails sent during the outage will arrive late. The Microsoft 365 service status page is the place to check for updates.

What this means for UK businesses

Most small and mid-sized firms run email, chat and shared files through one provider. That works well until it goes down. A few simple steps can keep you reachable on a day like this.

• Have a second way to reach staff. Agree on a phone group, text messages or another messaging app that does not rely on Microsoft 365, and make sure everyone knows to use it.
• Check your website forms and live chat. If form submissions are sent only to an Outlook inbox, they may be delayed or lost. Check where they are stored, and whether you can see them in your website's admin area.
• Tell customers about delays. Put a short notice on your website and social channels saying email replies may be slow, and give a phone number they can use instead.
• Watch the official status page. Microsoft's own updates are more reliable than rumours on social media.
• Review afterwards. Once service is back, check for missed messages and orders, and note what you would do differently next time.

Analysis compiled by Sayu (sayu.co.uk), based on news reports from AOL UK, ABC7, ABC News, CTV News and BleepingComputer.