Downdetector logged a peak of 130,000 Outlook complaints on Thursday afternoon. That single number captures the scale of the Microsoft 365 outage that began Thursday afternoon, hit Exchange Online hardest, and by early Friday had dragged Microsoft's stock down nearly 2.3% to $511 in premarket trading.

The disruption rippled across five distinct areas: Outlook email, three Indian airlines, AI integration tools from OpenAI and Anthropic, and Microsoft's share price. Here is how each one broke — and what it tells you about how much of the working world now sits on a single vendor's email plumbing.

What happened to Outlook email?

Users could not open their Outlook mailboxes, and email deliveries were delayed. Exchange Online is the email infrastructure behind Outlook — when it fails, two basic tasks break at once: getting into an inbox and getting a message to its recipient. Both stopped working for affected users.

The 130,000 complaint figure needs a caveat. Downdetector.com only counts people who chose to file a report. It measures visibility of the disruption, not how many people it actually reached.

The pain did not end at midnight. New reports were still arriving early Friday.

Microsoft's fix was mechanical: it lengthened the email timeout window to 48 hours. A timeout window sets how long a mail system keeps trying to deliver a message before giving up — once it closes, an undelivered message is typically returned to its sender as a failure. The longer window protects delayed messages while the company works through the backlog.

As of Microsoft's latest update, no estimate existed for when full email access would return for all users. Restoration work was ongoing.

How did Indian airlines get hit?

Three carriers — IndiGo, Akasa Air and Air India — reported direct effects, all through their customer-support email services, the part of Microsoft 365 that took the heaviest damage.

• IndiGo said its customer-support email service was disrupted, disclosing the problem publicly while the outage was still underway.
• Akasa Air reported the same disruption to its support inboxes.
• Air India took a different route. It temporarily redirected incoming emails so customer support could keep running, rather than waiting for normal service to return.

That places all three among the companies outside Microsoft that reported direct effects from the Outlook outage.

Why did OpenAI and Anthropic tools fail too?

Users of OpenAI's and Anthropic's Microsoft 365 integration tools — products built by those companies to work with Microsoft 365 services — reported failures during the outage.

OpenAI described two distinct failure modes:

• Attempts to make a new connection to Microsoft's services could fail.
• Tools with an existing connection might not behave as expected.

One warning covers anyone setting up a fresh link mid-disruption. The other covers already-connected tools acting unpredictably. Either way, the reports show the disruption reaching products Microsoft did not build.

What did the outage do to Microsoft's stock?

Shares fell nearly 2.3% to $511 in premarket trading early Friday — the early window before the regular U.S. session opens, where prices show where buyers and sellers stand ahead of the opening bell but are not a closing price. Microsoft trades on the Nasdaq under the ticker MSFT.

The Friday drop followed a quiet session: Microsoft closed Thursday almost flat at $523, meaning the stock was little changed on the day the email problems began.

Two things the numbers do not tell you. No cause beyond timing has been attributed to the premarket decline. And where the stock finished Friday has not been reported.

Context matters here. The decline arrived after a strong run — Microsoft shares are up nearly 28% over the last six months, a climb that began from significant lows recorded in the first half of the year.

What's the takeaway?

One failing service, Exchange Online, simultaneously broke corporate email, grounded three airlines' support desks, knocked third-party AI tools offline and shaved more than two percent off one of the world's most valuable companies. The backlog is still clearing. Until Microsoft restores full access, the 48-hour timeout window is the only thing standing between delayed mail and delivery failure.