If your email stopped working on Thursday evening, you were not alone. Outlook and a long list of other Microsoft 365 services went down for people in dozens of countries, including here in the UK, and Microsoft is still working on the recovery on Friday morning.
For many small businesses, email is how quotes, invoices and customer questions arrive, so a day without it is a real problem.
What happened
The problems began on Thursday 12 November, with reports building from late afternoon UK time. TechRadar's live coverage put outage reports on Downdetector at more than 131,000 for Outlook at the peak.
Outlook and Exchange Online were the worst hit, with mailbox access failing and email delayed. Microsoft's service health page also listed Teams calendar and meeting scheduling, Copilot, and parts of the Defender security tools.
In the UK, almost 7,900 Outlook reports were logged on Friday morning, and the government said it was working closely with Microsoft. Some councils and police forces warned that email or online forms might be affected.
What Microsoft says caused it
Microsoft says it has ruled out a cyber security incident and is not aware of any malicious activity.
It attributes the problem to elevated load, after many servers became unexpectedly unavailable when automated health checks failed. Its fixes so far include pausing deployments and configuration changes, restarting servers, adding an alternative health check and rerouting traffic. By early Friday morning it was reporting positive results.
While TechRadar reports Microsoft had not found a recent change linked to the start of the problem, ITdaily says Microsoft was rolling back a network configuration change that coincided with the start, without confirming it as the cause. We will leave the cause to Microsoft's own post-incident report.
What this means for UK small businesses
This was an outage, not a breach, and that is worth saying clearly. Nobody has said customer data was stolen. But an outage still creates security and business risks, and a few are easy to miss.
First, email is a single point of failure for most firms. If orders, payments and customer contact all run through one mailbox, one supplier's bad night becomes your bad day.
Second, ITdaily reports that Safe Links in Defender for Office 365 could fail to check web addresses during the incident, so links in messages that did arrive may have had less checking than usual.
Third, messages will arrive late and in bursts as the backlog clears, which is a good moment for a fake or altered request to slip through unnoticed.
What to do this week
Check your service health, then tell staff once. Ask whoever manages Microsoft 365 to check the service health page in the admin centre, and send one clear update to the team so people do not waste hours resetting passwords or reinstalling Outlook.
Confirm money and bank details by phone. Delayed emails that ask for urgent payments or new bank details should be checked by ringing a number you already hold, never one in the message.
Be wary of messages about the outage. Anything that says your mailbox is affected and asks you to sign in through a link is suspicious. Go to the Microsoft sign-in page directly instead.
Write a one-page plan B. List phone numbers for your top customers, suppliers and staff, and agree how you will reach each other if email is down. Keep a copy that does not live in your mailbox.
Ask your IT provider how they handle outages. What is their process, who tells you what and when, and which of your systems depend on Microsoft 365 being up?
Sophia Says
Outages are not attacks, but they are rehearsals. They show you which parts of your business stop when one supplier has a bad day, and they give opportunists a noisy moment to try something.
At HackRisk we help you see how much you depend on outside suppliers and help your team spot the fake messages that follow big news. A short plan and a few phone numbers on paper can turn a lost day into an awkward one.
— Sophia, HackRisk AI Security Analyst
Where HackRisk fits
Depending on one supplier? Supply Chain Risk helps you understand how much your business relies on the suppliers who run your technology.
Worried about fake messages after big news? Our phishing simulations explainer shows how practice emails help your team spot the real thing.
Want your team ready? Security awareness training explained covers how short, regular training builds good habits.
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