Thanks for reaching out to the Microsoft Q&A Forum. From your description, I understand that the left column in Outlook.com, with folders such as Inbox, Sent, and Deleted Items is missing, and you would like to restore it.
Please make sure you've already tried the Q&A Assist steps under your thread and you can refer to @EmilyS726's answer as well. If the issue persists after following those suggestions, please try the steps below:
- Refresh the Outlook.com page (https://outlook.live.com), sign out, and then sign back in to your account.
- Switch to a different browser or open a private/incognito window and sign in again to rule out a browser cache or extension issue.
- Reduce the browser zoom level to 100% and ensure the window is maximized, as a narrow screen width can automatically hide the folder list.
- Temporarily disable browser extensions, especially ad blockers or UI modifiers and reload Outlook.com.
I hope this helps! Please feel free to let me know how it goes and thank you for your understanding.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.