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Oasis Web Services

Security · 7 min read

Microsoft 365 Outage: What UK Businesses Should Do Now

Oasis Web Services
· Updated

A post room with its shutter down, letters piling up outside and a phone glowing in front

Picture arriving at the office to find the post room locked. Letters are still arriving, but nobody can reach them, and customers are wondering why you've gone quiet.

That's roughly what Thursday and Friday looked like for many businesses running email through Microsoft 365. And if your website contact form sends enquiries to a Microsoft 365 mailbox, this outage may have delayed leads you don't know about yet.

We'll be upfront about the gaps. Microsoft hasn't confirmed the root cause, and we couldn't find reliable UK-specific figures, so we've left out anything we can't back up.

What happened in the Microsoft 365 outage?

A large part of Microsoft 365 stopped working on Thursday 12 November, and recovery was still patchy on Friday. The problems began at around 1pm US Eastern time, which is 6pm in the UK (TechRadar, 2026 (opens in a new tab)). Outlook, Teams calendars and meeting scheduling, SharePoint (file sharing) and Copilot (Microsoft's AI assistant) were all affected, along with outside tools that connect to Microsoft 365 (CIO&Leader, 2026 (opens in a new tab)).

This was no minor wobble. Downdetector, a site that tracks user reports of outages, logged roughly 130,000 Outlook problem reports at the peak, with users affected in 74 countries (CIO&Leader, 2026 (opens in a new tab)).

Recovery has been bumpy. Microsoft stopped rolling out changes, steered work away from the struggling servers and restarted them. It then warned that restored servers could buckle again once normal traffic returned. By early Friday it reported early stabilisation, but said service health was still variable and capacity hadn't fully returned to normal (TechRadar, 2026 (opens in a new tab)).

What does Microsoft say caused it?

Microsoft says overloaded servers caused the outage, not a cyberattack, but it hasn't confirmed the root cause yet. Its explanation is that some servers failed and shifted their traffic onto the remaining ones, which then became overloaded (Forbes, 2026 (opens in a new tab)). Microsoft executive vice president Charles Lamanna has also said it wasn't a cyberattack (CIO&Leader, 2026 (opens in a new tab)).

"Root cause" simply means the original trigger. Microsoft has promised a Post-Incident Report with full root-cause details (Forbes, 2026 (opens in a new tab)). Until it lands, treat confident explanations on social media with caution.

Will my emails be lost?

Probably not, but some may arrive late. Microsoft said it would extend its email timeout window to 48 hours to help protect delayed messages while recovery continues (TechRadar, 2026 (opens in a new tab)). As we read it, that means delayed emails get up to 48 hours before they bounce back to the sender, so other people's mail systems should keep retrying delivery to you for longer.

Don't treat that as a guarantee. Microsoft hasn't said nothing will go missing, so for anything important, ask the sender to resend or confirm by phone. That bit's our advice, not Microsoft's.

What should UK businesses do during a Microsoft 365 outage?

Ring your key contacts, put a phone number on your website, and treat email as unreliable until Microsoft confirms recovery. In practice, that looks like this:

  1. Call, don't wait. ESET's Jake Moore advises relying on phone calls for anything urgent (Forbes, 2026 (opens in a new tab)).
  2. Move urgent chat elsewhere. Forbes suggests WhatsApp, Signal or Slack as stopgaps while Outlook and Teams are unavailable (Forbes, 2026 (opens in a new tab)). The same idea may help a small team, but one tip of ours: avoid sending sensitive customer data through an app your business hasn't approved.
  3. Follow Microsoft's updates. Microsoft is posting progress on its Microsoft 365 Status account on social media (ABC News, 2026 (opens in a new tab)). If you contact your IT support, quote the incident numbers: EX1550543 for Exchange Online (the engine behind Outlook email) and MO1550821 for the wider Microsoft 365 problem (CIO&Leader, 2026 (opens in a new tab)).
  4. Put a holding message on your website. One short line is enough, such as "We're having email problems, please ring us on (your number)." A website is often hosted separately from email, so it may be the one place you can still reach customers.
  5. Offer a second way to enquire. A phone number, or a contact form that doesn't depend on a single mailbox, means new customers can still reach you.
  6. Be wary of "fix" emails. Treat unexpected messages claiming to repair the outage with suspicion, and go straight to Microsoft's own pages instead.

How can you prepare before the next outage?

Write a one-page outage plan once things have settled. The NCSC, the UK's National Cyber Security Centre, says you should have tested incident response processes that cover wider service outages, not just problems with your own account, and keep critical data in at least one resilient backup, meaning a copy stored somewhere separate (NCSC cloud security guidance (opens in a new tab)).

For a small business, a sensible plan covers:

  • Mobile numbers for key staff and your most important customers, kept somewhere that isn't your email.
  • A second route for customers to reach you, such as a phone number on your website.
  • Who speaks to customers during an outage, and what they say.
  • Where your important data lives, and whether a separate backup exists.
  • A quick test now and then: pretend email is down for an afternoon and see what breaks.

Moore also warns that relying on a handful of big vendors can turn one failure into widespread disruption (Forbes, 2026 (opens in a new tab)).

Is your website contact form affected?

It can be: if your form delivers to a Microsoft 365 mailbox, enquiries may arrive late or sit unseen until recovery. That's our view, and it's the main lesson we'd take from this week: your website shouldn't depend on a single inbox.

We're not telling you to ditch Microsoft 365. Every cloud service has a bad day. The useful question is what your customers see while it's down. A visible phone number, a clear holding message and a second route for enquiries are usually quick to put in place and can help keep the shop door open.

We can't promise any setup will never fail. What we can do is help reduce the chance that one failure leaves your customers staring at silence.

FAQ

Is the Microsoft 365 outage over?

At the time of writing on Friday 13 November, not fully. Microsoft reported early stabilisation and, by late morning UK time, improvements in mailbox access and delayed email, but said some intermittent issues may continue. Check Microsoft's status account for the latest, as this answer will date quickly.

Was the Microsoft 365 outage a cyberattack?

Microsoft says no. It has said there's no indication of malicious or cyber activity, and attributes the outage to servers becoming overloaded after others failed. The root cause hasn't been confirmed, and Microsoft has promised a Post-Incident Report with full root-cause details.

What should I do if I can't access my business email?

Ring your most urgent contacts, switch urgent chat to an approved alternative, and add a holding message with a phone number to your website. Ask important senders to resend later, as delayed messages may still arrive once service recovers, though Microsoft hasn't guaranteed that.

Can my website keep working when Microsoft 365 is down?

Often, because websites and Microsoft email are usually separate services, though that's our general understanding rather than a Microsoft statement. The catch is any contact form that sends enquiries to a Microsoft 365 mailbox, as those messages may arrive late. Check how your form delivers, and consider a second route.

How we can help

If you'd like a second pair of eyes on how your contact form delivers, we're happy to take a look. That might lead to a clear notice banner, a second route for enquiries, or a maintenance plan so someone is keeping an eye on things. There's no rush while things settle.

Get a free quote whenever suits you.

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