Microsoft 365 outage: Exchange Online disruption of 12-13 November 2026

What happened in the Microsoft 365 outage?

A Microsoft 365 outage that began on Thursday 12 November 2026 left many users unable to reach Exchange Online mailboxes, first in the Americas and later, Microsoft said, in any region. Microsoft says it was a technical fault, not a cyber attack, tied to a network capacity upgrade. As of 13 November, recovery was under way but not confirmed complete.

That is the short version. The detail below separates what Microsoft and the outlets we checked have confirmed from what remains unknown.

Timeline: when did the outage start and how did it develop?

BleepingComputer reports that Microsoft gave the start of the main incident as 1:26 PM ET on Thursday 12 November. CNBC says connectivity problems began shortly before 1 PM ET that day. The two accounts are close but not identical, so treat the start time as approximate.

One source gives a different figure. Search Engine Roundtable says the Microsoft Advertising status page lists 7:15 AM EST on 12 November, while the article text says "around noon". We could not load the status page itself (it returned no incident listings to our fetch), so we have not used the earlier time.

Updates reported by BleepingComputer, all in Eastern Time:

When	What Microsoft said
12 November, 6:57 PM	Limited recovery after some servers returned to service
13 November, 8:05 AM	Gradual recovery; email timeout window extended to 48 hours
13 November, 12:06 PM	Email queues significantly reduced and approaching normal levels; some users may still see intermittent access problems or delayed delivery

Search Engine Roundtable, writing on the afternoon of 13 November, described the situation as improving but not fully resolved after about 24 hours. We did not find a Microsoft statement declaring full restoration. Microsoft's Office status page, which it pointed people to for confirmation, returned no readable incident detail to us.

Which services were affected?

Exchange Online was the centre of the problem. BleepingComputer lists Microsoft's advisory MO1550821 as covering Exchange Online, Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR. CNBC also names Outlook, Teams, SharePoint and Copilot. Search Engine Roundtable cites the incident ID EX1550543 for the mailbox problem. The different identifiers appear to be separate advisories for related symptoms, but we have not seen Microsoft explain how they relate.

BleepingComputer also notes a shorter Teams incident, TM1550488, on the morning of 12 November (9:45 to 10:53 AM ET), attributed by Microsoft to resource contention. Microsoft has not said whether it is linked to the larger outage.

What caused it?

Microsoft's public line, as relayed by CNBC and Search Engine Roundtable, is that the problem began during an earlier network capacity upgrade and surfaced after a recent network change. It described the incident as a technical issue, not related to cyber activity or AI agents, and said it had no indication of malicious activity.

The explanation shifted as the day went on, according to BleepingComputer:

• Microsoft first pointed to elevated infrastructure load.
• It then said a number of servers being unexpectedly unavailable had strained the remaining infrastructure.
• A later update said a core process on affected servers became overwhelmed, causing a loss of capacity.

BleepingComputer adds that the underlying reason the servers failed has not been disclosed. Microsoft has promised a full report once its review is complete.

How did Microsoft respond?

According to BleepingComputer, Microsoft paused deployments, redistributed traffic, moved traffic away from affected systems, restarted servers and examined whether reverting a small number of recent configuration changes would speed recovery. CNBC reports that Microsoft restored systems in stages and apologised: "We are deeply sorry for the disruption this incident has caused our customers and partners."

Search Engine Roundtable adds that Microsoft said staged restoration, with stability checked at each step, lengthened the recovery.

Did the Microsoft 365 outage affect Microsoft Advertising?

Indirectly, at most. Search Engine Roundtable reports that Microsoft Ads Liaison Navah Hopkins said on LinkedIn that Microsoft Advertising was not directly affected. Her suggestion was that Outlook ad requests may have been weak because some people could not load Outlook, which could have touched some advertiser spend. The Microsoft Advertising status page (post 5624) lists ad delivery as affected but states that platform and delivery health were not impacted, according to the same report. Treat that as Microsoft's characterisation, not a measured figure.

Analysis: what should IT teams take from it?

This section is our own reading, not a Microsoft statement.

First, the pattern matters more than the label. A fault that starts in routine infrastructure work and then spreads is harder to contain than a single failed component, and the staged recovery described here fits that. Second, the 48-hour email retry window is the detail most likely to protect ordinary users: messages that were delayed rather than rejected should arrive once queues clear, though that is Microsoft's stated behaviour and not a guarantee for every sender.

Practical steps for administrators, based on general good practice rather than anything Microsoft advised:

• Check the Service health page in the Microsoft 365 admin center for your tenant's incident entries.
• Tell staff that delayed mail is expected before they resend important messages.
• Keep an out-of-band channel for urgent communication when email is down.

Microsoft has also been in the news for administrators this week over the KB5132061 install failures in the November Windows 11 update and the SQL Server linked server bug in the October Windows update. Those are separate issues and there is no stated link to this outage.

What is still unknown?

• Whether full restoration has been declared across all regions and tenants.
• Why the servers became unavailable in the first place.
• How the separate incident IDs relate to each other.
• How many customers were affected: none of the sources we opened gave a figure.

Sources

• Search Engine Roundtable: Microsoft 365 outages and Microsoft Ads
• BleepingComputer: Massive Microsoft 365 outage disrupts Outlook, Teams, Copilot worldwide
• CNBC: Microsoft apologizes for massive outage that took down Outlook and other 365 services
• Microsoft Advertising platform health
• Microsoft service health status