Using New Outlook on Windows for personal email, calendar, and contact management
To stay signed in with Outlook.com in a web browser, simply sign in normally with the Microsoft account username and password and do not sign out when finished.
Starting in February 2025, the web browser sign-in experience for Microsoft accounts changes so that the session stays signed in automatically unless signing out manually or using a private browsing window. On a personal computer, the browser will remember the sign-in information and keep the Outlook.com session active.
On shared or public devices, use a private browsing window instead so the account does not remain signed in and others cannot access Outlook.com, OneDrive, or the browsing history.
To sign out when needed, select the profile picture in Outlook.com and choose Sign out.
References: