Configuring preferences and options in Outlook.com
You cannot access non-Microsoft accounts in outlook.com on the web. It is only for Outlook.com / Hotmail addresses. If you like the Outlook web interface, you can use the new Outlook app, it uses the same scripts and supports IMAP accounts.
Microsoft used to have an option to link non-Microsoft accounts to an outlook.com mailbox but that program ended July 1 2024.