Using New Outlook on Windows for personal email, calendar, and contact management
Hi, Rajkumar V
This may have been caused by an Inbox rule, Sweep setting, or another mail app connected to the account. Since an entire date range moved at once, it is worth checking the mailbox settings before restoring everything.
Here are some suggestions you can try:
Sign in to Outlook on the web, then go to Settings > Mail > Rules. Disable or remove any rule that moves or deletes messages. Rules can process messages automatically as soon as they arrive. Manage email rules in Outlook
Check Settings > Mail > Sweep and remove any automatic cleanup action that you do not recognize. Sweep can automatically move or delete messages from selected senders. Review Sweep settings
Temporarily close Outlook and other mail apps on phones or tablets. Move one test email back using Deleted Items > select the message > Move > Inbox. If it remains there in Outlook on the web, another connected app or device may be moving the messages.
Once the cause is stopped, select the affected 2026 emails in Deleted Items and move them to Inbox in batches. Restore deleted Outlook messages
If you find an unfamiliar rule, also change the account password and review recent sign-in activity.
Thank you for your patience in reading, I hope this information has been helpful to you.
If the answer is helpful, please click "Yes" 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.