If your office spent Thursday afternoon refreshing Outlook, you were not alone. A global Microsoft 365 outage knocked out email for millions of people, dragged Teams, SharePoint, and Copilot down with it, and was still not fully resolved when the Friday workday started on the East Coast.
I have been doing this for more than 25 years, 15 of them running a managed service provider, and I have watched every major cloud platform have a bad day. Outages like this one are not a reason to panic or to rip out Microsoft 365. They are a reason to decide, before the next one, what your business does when the tools everyone depends on stop answering.
Below is what we know about the November 12 Microsoft outage so far, what it means for your email and your contract with Microsoft, and a practical playbook for keeping a 15 to 75 person company working the next time it happens.
What happened during the November 12 Microsoft 365 outage
Problems started on Thursday, November 12. Microsoft first posted that it was investigating reports of users having trouble reaching their mailboxes shortly before 1 p.m. Eastern, and it later said the disruption itself began at 11:17 a.m. ET in Exchange Online, the service that runs Outlook email.
Microsoft tracked the event in the Microsoft 365 admin center under advisory MO1550821, which listed Exchange Online, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot, and Microsoft Defender XDR as services customers might not be able to connect to. The Exchange side ran under incident EX1550543, and an earlier Teams problem in North America ran under TM1550488. As the night went on, the list of possibly affected services grew to include Planner, To Do, Purview, Intune, and Defender for Office 365.
The scale was hard to miss. Downdetector logged reports from 74 countries and territories within about an hour. Outlook alone drew nearly 130,000 reports in the United States at its peak, and across five Microsoft services Downdetector saw 19,650 reports per minute at the peak, compared with fewer than 15 on a typical Thursday.
What Microsoft has said about the cause
As of Friday morning, Microsoft has not published a root cause. Here is what its updates have said so far:
- It first pointed to elevated load, then corrected itself: a number of servers had become unexpectedly unavailable, straining the remaining infrastructure.
- Around 4 p.m. ET Thursday, it said an alternative health check had returned some servers to service. About an hour later it said those recovery actions had not delivered the expected relief, and that restored servers stopped responding once traffic returned.
- Overnight it said a process on the affected servers that sets up secure connections was being overwhelmed, and that it was reverting a recent network change. Neither has been confirmed as the root cause.
- By Friday it had rolled out a targeted configuration update to keep critical workloads online, and it reported encouraging recovery progress, with intermittent issues still expected.
Microsoft also said it found no indication this was the result of malicious or cyber activity. It has said it will publish the root cause and its repair items in a post-incident report once the issue is mitigated. Until that report comes out, anyone who tells you exactly why this happened is guessing.
Why an Outlook outage took down Teams, Copilot, and security tools
A lot of business owners asked us some version of the same question on Thursday: why would an email problem break Teams?
Microsoft 365 is not a set of separate apps. It is one platform with Exchange Online underneath a surprising number of features. Teams calendars and meeting invites live in Exchange mailboxes. Copilot reads your mail and calendar to answer questions. Defender and Purview inspect mail flow. When Exchange stops accepting connections, everything that leans on it stumbles, even if the app itself is technically up.
That also explains why some things kept working. Reporting from Al Jazeera noted that Teams chats and calls largely kept working, and desktop Outlook could still show email that had already downloaded. That detail matters for the playbook later in this post.
Was any email lost?
Probably not, but a lot of it was late. Email was designed for exactly this kind of failure. When a receiving mail server is unavailable, the sending server is supposed to keep the message in a queue and try again. The SMTP standard says the give-up time generally needs to be at least 4 to 5 days, although many modern senders give up sooner.
Microsoft added a safety margin of its own. It said it was prioritizing queue and backlog processing and that the email timeout window had been extended to 48 hours to preserve delayed messages. One email deliverability firm that tracked the incident reported that mail sent to Microsoft during the outage was deferred with temporary errors, not rejected.
Three practical takeaways:
- Expect a flood, not a gap. As queues drain, staff may see hours of mail arrive at once, out of order. Tell them before it happens.
- Watch for bounces on outbound mail. Exchange Online normally retries a deferred outbound message for 24 hours before it returns a non-delivery report. If anyone on your team gets a bounce for something they sent Thursday, have them resend it.
- Confirm anything time-sensitive by phone. If a contract, a court filing, a closing document, or a payment confirmation was due Thursday, do not assume it arrived. Call.
This was not the first Microsoft 365 outage of 2026
It would be easy to treat Thursday as a freak event. The record says otherwise. In January, a Microsoft 365 outage dragged on for nearly 10 hours and hit Outlook across North America. Microsoft’s own quarterly uptime number for the first quarter of 2026 came in at 99.526 percent, the lowest figure since tracking began in 2013, roughly 614 minutes of interruption.
Microsoft 365 is still far more dependable for most of my clients than the on-premises Exchange servers it replaced. But “Microsoft runs it, so it never goes down” is not a business continuity plan.
What does Microsoft owe you after an outage like this?
Less than most owners think. Microsoft’s commitment is 99.9 percent uptime, measured per service and per month. For Exchange Online, the current Service Level Agreement for Online Services (October 2026 edition) counts downtime as any period when users cannot send or receive email with Outlook on the web, multiplied by the number of users affected. If uptime for your organization falls below the line, you can claim a credit on that service’s monthly fee: 25 percent below 99.9 percent, 50 percent below 99 percent, and 100 percent below 95 percent.
A few realities to keep in mind:
- 99.9 percent still allows about 43 minutes of downtime in a 30-day month without any breach. An outage that lasted most of a business day for your users would clear that bar easily.
- Credits are not automatic. Under the SLA, you have to submit a claim to Microsoft support with a description of the incident, the time and duration of the downtime, and the number and location of affected users. Missing information gets claims rejected.
- There is a deadline. For Microsoft 365 services, Microsoft must receive the claim by the end of the month after the incident, so for this outage that means by December 31.
- The credit is a discount on a subscription, not compensation. If your team of 30 lost an afternoon of billable work, a 25 percent credit on one month of Exchange Online will not come close to covering it.
File the claim anyway if you were affected. Just do not mistake the SLA for a safety net. The only thing that protects your business during an outage is what you planned before it.
The honest part: you cannot make Microsoft more reliable
No setting, license, or IT provider can stop a Microsoft data center problem from reaching your tenant. Anyone selling you a product that “prevents Microsoft 365 outages” is overselling.
What you can control is how much an outage costs you. That comes down to four things: how fast you find out, whether your people can still reach each other, whether they can keep working on what matters most, and whether anyone takes advantage of the confusion. The playbook below is organized around those four things.
A continuity playbook for the next Microsoft 365 outage
1. Find out before your staff do
On Thursday, many offices learned about the outage when the receptionist said Outlook was broken, and then lost an hour to people restarting laptops. Set up three things now:
- Service health email alerts. In the Microsoft 365 admin center, Service health has a Customize option where you can sign up for email notifications of new incidents and status changes. Send them to at least one address that is not hosted in Microsoft 365, such as a personal Gmail account for the owner or office manager. Otherwise the alert about your email being down gets delivered to your email.
- The Microsoft 365 Admin app. Microsoft notes you can use the Microsoft 365 Admin mobile app to view Service health with push notifications.
- The backup status page. When the admin center itself is affected, Microsoft posts updates at status.cloud.microsoft, which it describes as a backup notification page. Bookmark it on your phone.
2. Have a way to talk to each other that does not run through Microsoft
If your entire internal communication plan is email and Teams, an outage like this one leaves you with nothing. You do not need an expensive second platform. You need a channel that is set up and tested before you need it:
- A group text or messaging thread on personal phones for managers, with the owner’s consent and a clear rule that it is for outages and emergencies only.
- A short phone tree for the people who have to make decisions.
- Personal phone numbers for key clients and vendors stored somewhere other than Outlook contacts, such as a printed sheet or a password manager entry.
One caution: if your business phones run through Teams Phone, they share the same platform. Teams calls largely held up on Thursday, but I would not build a plan around that being true next time.
3. Keep the critical work available offline
The quickest win in this whole post is making sure your most important files are on the device, not just in the cloud. OneDrive lets users right-click a file or folder and choose Always keep on this device, which downloads it and keeps it available offline. Do this for the handful of folders each role cannot live without: current client files, price sheets, the schedule, the procedures binder.
The same idea applies to email. Desktop Outlook keeps a local copy of mail that has already synced, which is why some people could still read and search older messages on Thursday while Outlook on the web was dead. If your team works mostly in the browser, they had nothing. If you are not sure where your company files actually live, our post on SharePoint vs OneDrive walks through it.
4. Decide whether email continuity is worth paying for
For some businesses, a day without sending or receiving email is an inconvenience. For others, such as a firm with filing deadlines or a practice that schedules by email, it is a real financial event. Several email security gateways that sit in front of Microsoft 365 offer a continuity add-on. When Microsoft is down, the gateway holds your inbound mail and gives users an emergency web inbox so they can keep reading and sending from their normal addresses.
My honest view: most offices of 15 to 30 people do not need it, and a written runbook plus offline files covers them. If a single day without email would cost you more than a year of the add-on, price it out. If you already pay for a filtering service, ask whether continuity is included or available. Our post on email filtering for small businesses covers how those gateways work.
5. Write a one-page outage runbook
Thursday’s outage started around midday and ran into the next business day. A runbook answers the questions everyone was asking without having to wait for the owner:
- Who declares an outage, and how do they tell everyone (see step 2)?
- What is our minimum viable service? Which three things must keep happening (answering phones, seeing patients, meeting a deadline) and how do we do them without email?
- What do we tell customers? Keep a two-sentence message ready for your phone greeting, website banner, and social accounts.
- What do staff do while they wait? Offline work, phone calls, paper processes. Not 40 people rebooting laptops.
- Who checks the backlog afterward and confirms nothing time-sensitive was missed?
If you want a starting point, our business continuity plan template covers this and the larger events like hurricanes and ransomware. An email outage is just a smaller version of the same exercise.
6. Do not make it worse with local fixes
When Outlook breaks, the instinct is to fix it locally. During a platform outage that only adds damage. Guidance published during the incident recommended avoiding password resets, Outlook reinstalls, and profile rebuilds, which cannot fix a data center capacity problem.
The rule for your team is simple: if Microsoft has confirmed an incident, stop troubleshooting and switch to the runbook.
7. Expect the scammers
Every large outage is followed by phishing that uses it as cover. Security researchers have seen fake “service restoration” emails and texts that claim users must sign in again show up within hours of major Microsoft, Google, and AWS outages. Over the next week, assume any message about your Microsoft account, password, or a “recovered” mailbox is suspicious until verified.
Tell your staff today: Microsoft will not email them asking them to sign in to restore their mailbox, and IT will not call asking for an MFA code. Our posts on what social engineering looks like inside a small business and business email compromise are worth sharing with your team this week.
8. Keep backups and outages in separate boxes
An outage and a data loss are different problems. On Thursday your data was not gone; you just could not reach it. Backups of Microsoft 365 protect you from deletion, ransomware, and departed employees, which Microsoft’s own retention does not fully cover. Our posts on what really happens when you lose data in Microsoft 365 and the 3-2-1 backup rule explain why.
9. Document the impact and claim your credit
While it is fresh, write down which services your team lost, for how long, and what it cost: missed appointments, delayed invoices, overtime. You will need it for the SLA claim, and you will need it in six months when you are deciding whether that continuity add-on is worth the money.
What I would not do
- Switch platforms because of one outage. Every major cloud provider has outages. If you are weighing a move for other reasons, our Google Workspace vs Microsoft 365 comparison is a better place to start than Thursday’s headlines.
- Build a full second email system. Running two platforms in parallel doubles your cost and your security exposure for a problem that, so far, happens a few times a year.
- Bring the email server back in-house. An on-premises Exchange server in a closet is far more likely to go down than Microsoft 365, and when it does, nobody publishes a status page.
Where I have a stake in this
Harmony MSP manages Microsoft 365 for small and midsize businesses, and helping clients plan for outages is part of what we do. We do not earn anything from Microsoft based on which plan you buy for this purpose, and we do not resell email continuity add-ons on commission. Nothing in this post requires hiring us; the free steps (alerts, offline files, a runbook, and a scam warning to staff) are where most of the value is.
Microsoft 365 outage FAQ
Is Microsoft 365 still down?
As of Friday morning, November 13, Microsoft reported encouraging recovery progress but had not declared the incident resolved, and some users were still seeing intermittent problems. Check status.cloud.microsoft or Service health in your admin center for the current status of your tenant.
Did the Microsoft outage delete my emails?
There is no indication it did. Mail sent to Microsoft 365 during the outage was deferred and queued, and Microsoft extended its email timeout window to 48 hours to protect delayed messages. Expect late mail to arrive in bulk as recovery continues, and resend anything that bounced.
Was the November 12 outage a cyberattack?
Microsoft has said there is no indication the outage was caused by malicious or cyber activity. It has not yet published a root cause and has said a post-incident report will follow.
Where to start
If you do one thing today, set up Service health alerts to an address outside Microsoft 365 and send your staff a two-line warning about restoration scams. If you do three things this month, add offline files for critical folders and a one-page outage runbook.
If you would like a second set of eyes on how your office would get through the next Microsoft 365 outage, we are happy to talk it through, no pressure and no obligation. Give us a call at (407) 720-6540, or learn more about how we support small and midsize businesses and provide IT support in Orlando.
Sources
- BleepingComputer, “Massive Microsoft 365 outage disrupts Outlook, Teams, Copilot worldwide,” Nov 12, 2026
- CNBC, “Microsoft outage continues, Outlook and other 365 services down,” Nov 12 to 13, 2026
- ABC News, “Microsoft Outlook outage updates,” Nov 13, 2026
- Al Jazeera, “Microsoft hit by global outages: What happened and why?” Nov 13, 2026
- IBTimes, “Microsoft Outage Disrupts Work Across The Globe,” Nov 13, 2026
- Windows Forum, “Microsoft 365 Outage MO1550821” megathread, Nov 12 to 13, 2026
- Windows Forum, “Microsoft 365 Outage Investigation: Secure Connection Overload and Network Rollback,” Nov 13, 2026
- Petri, “Microsoft Deploys Patch to Stabilize Microsoft 365 Outage,” Nov 13, 2026
- DMARCguard, “Microsoft Outage EX1550543: Email Deferred, Not Rejected,” Nov 13, 2026
- IETF, RFC 5321, Section 4.5.4.1, Sending Strategy
- The Register, “Microsoft 365 outage drags on for nearly 10 hours,” Jan 23, 2026
- Office 365 for IT Pros, “Microsoft 365 uptime,” Apr 22, 2026
- Microsoft, Service Level Agreements (SLA) for Online Services (October 2026 English edition)
- Microsoft Learn, “How to check Microsoft 365 service health”
- Microsoft Learn, “Microsoft 365 Incident Readiness”
- Microsoft 365 Service health status page
- Microsoft Support, “Save disk space with OneDrive Files On-Demand for Windows”
- McAfee, “Today’s Microsoft Outage Explained and Why it Triggers a Scam Playbook,” Jan 22, 2026
