Microsoft's Office 365 has broken, leaving people unable to access their email.
The problems have run throughout the day, leaving people unable to work or communicate with colleagues.
People took to social media to complain about intermittent outages which left customers across Europe unable to send or receive emails.
The exact cause of the problem remains unclear, as Microsoft continues to seek a solution.
The trouble has been particularly frustrating for businesses unable to carry out day-to-day communication, with issues emerging as many people started work this morning.
"We're working to resolve difficulties some customers in Europe are experiencing when attempting to access Exchange Online," a Microsoft spokeswoman said.
"Admins can find status updates on the Admin Centre."
Additional reporting by Press Association
