Sending, receiving, and organizing email in Outlook.com
Hello, thank you for reaching out to Microsoft Q&A.
Could you please let me know the exact error message you receive when signing in with your Microsoft account on https://outlook.live.com/ online?
I successfully signed in with my personal Microsoft account (@outlook.com) on both the website and the app without any issues.
I recommend trying to use a private browsing tab or a different network to see if you can access all of your email messages normally. If there are any outages, you can check Microsoft’s Service Health status page for updates.
https://portal.office.com/servicestatus
Let me know how it goes.