Using Classic Outlook on Windows for personal email, calendar, and contact management
Hello, Pippa.
This is due to the recent global outage of Microsoft services. The outage affected office and postal services. Microsoft is working on a solution to the problem. You can track detailed information about the failure and the status of the services here.: https://status.cloud.microsoft/m365/referrer=serviceStatusRedirect (see "Microsoft consumer products" at the bottom of the page)