Around 6:30 p.m. Spanish time this Thursday, thousands of users began to notice that some Microsoft services were working poorly. The company quickly opened two incidents with rare codes: EX1550543 and MO1550821. These codes referred to problems in Exchange Online and Microsoft 365, which include a lot of everyday services for Microsoft users: especially Outlook email, but also Teams applications, a multi-service platform for work, and Copilot, the company's artificial intelligence agent.
The drop coincides with the recent global announcement of voluntary departures that Microsoft made for 60,000 of its workers, the equivalent of 27% of its workforce.
The first tweet from Microsoft where it admits the problem is from 6:54 p.m. and refers to problems in “the Americas.” An hour later it was in “any region” of the world. Spain, at the moment, is not one of the most affected, according to the Administration.
1/ What exactly happened
As Microsoft has explained so far, the main problem was excess load on some servers because others stopped working. For some reason that is still not completely clarified, the system closed servers because they did not pass controls and that caused those that were still active to be saturated. Microsoft stopped all configuration changes to prevent more servers from shutting down.
Because? Already at night in Spain, Microsoft pointed out the possible reason: "Our investigation has determined that a process on the affected servers, responsible for establishing secure connections, becomes saturated, which causes the servers to stop processing requests." When someone opens Outlook, their device and the server exchange an encrypted connection, but for some reason they don't understand each other and it crashes. That crash affected many servers, leading others to crash due to excess traffic.
That was the diagnosis. But figuring out what the cause was and how to fix it was not so easy. They tried changing configurations and undoing changes they had recently made. When several solutions are applied at once, the cause may not be as clear.
2/ Why isn't it solved then?
Because the servers are blocked again when they receive traffic. “Servers that we have returned to service may still not respond once they receive traffic,” Microsoft wrote in the morning. Hours later they were still the same: "We have checked the status of the changes applied to improve services and we confirmed that they do not work as expected."
Already at midday in Spain they were beginning to see some light, after pointing out “a gradual improvement in several services”: “We are observing improvements in key scenarios, including access to mailboxes and the processing of delayed emails, although some intermittent problems persist.” There is no complete solution at the moment.
Outages in Microsoft services are more common than it seems: they are usually due to a configuration change or an own failure. The strange thing here is that the patches don't hold together. To know more details we will have to wait for official explanations.
3/ Wasn't it a cyber attack?
At 4 a.m. in Spain, a Microsoft vice president, Charles Lamanna, published in X that the causes were not unrelated: "I can confirm that there is no indication that this is the result of malicious activity or a cyberattack." It is the only explanation that Microsoft has given at the moment outside the usual channel of its official website.
4/ This has happened before
Microsoft has had other big falls in recent years. The biggest due to the impact on airports on July 19, 2024. That was not really Microsoft's fault. CrowdStrike, a large cybersecurity provider, issued a faulty update that caused the famous blue screen on millions of Windows computers. The failure was corrected in just over an hour, but each affected machine had to be repaired one by one, so recovery took days. Thousands of flights were canceled around the world and banks, hospitals, shops and television stations were paralyzed.
A year later, on October 29, 2025, Microsoft was down for 8 hours in the afternoon in Europe. The cause was an inadvertent configuration change in Azure, the company's cloud. Xbox Live and Microsoft 365 fell, but also critical airline, bank and retail systems, with Alaska Airlines and Starbucks among the most cited names. Microsoft's final review ruled out a cyberattack. That case was notable because it came just nine days after a major outage of Amazon Web Services, Amazon's cloud.
5/ How many are affected?
