If your email stopped working on Thursday, it wasn't just you, and it wasn't your computer. Microsoft 365 had a major worldwide outage, and for many offices the trouble continued into Friday morning.
What happened
On Thursday morning, Microsoft began investigating reports that people in North and South America couldn't connect to their Exchange Online mailboxes, the service behind Outlook email in Microsoft 365. By early afternoon Eastern time, Microsoft had opened a broader incident covering Exchange Online, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender, and said users in any region could be affected.
Because so many Microsoft 365 features depend on email, the problem spread. Microsoft said the parts of its services that don't rely on Exchange Online kept working, but anything that touches mailboxes, calendars or email delivery was affected.
A separate, shorter Teams problem earlier the same morning caused message delays for about an hour. Microsoft says that one was fully resolved, and it hasn't said whether the two were related.
What caused it
Microsoft says the outage was not caused by more people using the service. Instead, a number of its own servers became unavailable, which overloaded the ones that were left. Over the course of the day it said a process that sets up secure connections on those servers was getting overwhelmed, and it began rolling back a recent network configuration change that lined up with the start of the problem.
Microsoft also says there is no evidence of a cyberattack or malicious activity. It has promised a full report on the root cause once the problem is completely fixed.
Where things stand
As of Friday morning, Microsoft reports steady recovery: email access and delivery are improving, and many messages that were stuck on Thursday are now arriving. Some people may still see intermittent errors while the last servers are brought back. Microsoft hasn't yet declared the incident fully resolved.
One helpful detail: Microsoft extended how long it holds undelivered email to 48 hours, so messages sent to you during the outage should still arrive rather than bounce. If you sent an important email on Thursday afternoon and haven't heard back, it's worth a quick phone call to confirm it got through before sending it again.
Where to check if Microsoft is down
When Outlook or Teams stops working, the first question is whether the problem is yours or Microsoft's. A few quick places to look:
- Microsoft's public status page: status.cloud.microsoft shows major Microsoft 365 problems and doesn't require you to sign in.
- Service health in the admin center: Whoever manages your Microsoft 365 account can see detailed incident notes there. Thursday's were tracked as MO1550821 (Microsoft 365) and EX1550543 (Exchange Online).
- Ask a coworker: If nobody in the office can get email, it's almost certainly not your computer. Restarting or reinstalling Outlook won't fix a Microsoft outage, so save yourself the trouble.
A simple outage plan for your office
You can't stop Microsoft from having a bad day, but a little planning keeps your business moving when it does:
- Keep a phone list. Have phone numbers for your key clients, vendors and staff somewhere other than Outlook, such as a printed sheet or your phone's contacts.
- Have a backup way to talk to your team. A group text or a quick phone tree works fine when Teams is down.
- Keep important files available offline. OneDrive can keep selected files on your computer so you can still open them when the cloud is slow.
- Tell clients early. If email is down for hours, a short message on your website or social media, or a few phone calls, saves confusion.
- Know who to call. Decide ahead of time who checks the status page and lets everyone know what's going on.
How we can help
When Microsoft has a problem, there isn't much anyone can do but wait, but you shouldn't have to figure out on your own whether the problem is Microsoft or your office. ProIT can check Microsoft's service health for you and tell you quickly what's going on. If you'd like help putting together a simple outage plan, or if email still isn't working right for you after Microsoft's recovery, contact us or call (480) 382-3289.
Sources: Massive Microsoft 365 outage disrupts Outlook, Teams, Copilot worldwide (BleepingComputer), Microsoft 365 Outage Disrupts Outlook, Exchange Online and Teams (SecurityWeek), and Was the Microsoft 365 outage a hack? (Windows Latest)