The issue is thought to have started around 8am. More than 80% of reported problems involved Outlook, when the email application is accessed through the web.
Microsoft has said it has started to “deploy a fix” after users reported problems with Outlook and Teams.
The technology giant said on Monday that users had been impacted due to a “recent change” to its Exchange Online programme.
The issue meant users struggled to send or load attachments to emails when using Outlook, were unable to connect to the server, and in some cases could not log into their accounts.
Microsoft Exchange Online is a platform for business communication that has a mail server and cloud apps for email, contacts, and calendars.
In a post on X on Monday afternoon, Microsoft 365 Status said it had reverted the change and “started to deploy a fix which is currently progressing through the affected environment”.
It added: “While this progresses, we’re beginning manual restarts on a subset of machines that are in an unhealthy state.”
By 2pm Microsoft’s own service status website said all systems were running normally.
Down Detector, a website that tracks outages, said tech problems started at approximately 8am.
Users from the UK and around Europe took to social media to report they were having problems accessing the platform.
One user wrote: “When you need to check an important mail, but #outlook decides to not work…”
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While another added: “Here in Belgium mainly issues with tracking of e-mail in Dynamics 365. Inbound and outbound in Outlook still work.”
Microsoft directed affected users to its admin centre, a page that is intended for those who have access to business networks and other professionals who manage IT networks. The page requires a login.
