Try these checks in Outlook.com:
- Check whether mailbox or cloud storage is full. If Microsoft cloud storage is full, Outlook.com cannot send or receive email, and messages sent during that time are bounced back to the sender and are unrecoverable.
- In Outlook.com, check the Other tab and make sure filters are not hiding messages.
- Check the Junk Email folder and Junk Email settings. If a message is there by mistake, mark it as not junk.
- Check whether messages are sorted oddly. Select Filter > Sort > Date to restore chronological order.
- Check whether email forwarding is enabled.
- Check whether any email rules are moving messages out of the Inbox.
- Check Deleted Items and Archive in case messages were moved there. In Deleted Items, use Recover items deleted from this folder if needed.
- If the account password was changed recently, update it. If the account was temporarily blocked because of unusual sign-in activity, unblock the Outlook.com account.
- If mail is missing only on one device, remove the partnership between that mobile device and the mailbox to fix sync issues.
- If concerned about account compromise, review recent sign-in activity for the Microsoft account.
If a specific sender’s messages are missing and there is no visible error, ask that sender to check Sender Support in Outlook.com.
If these steps do not help, use Outlook.com support from Help on the menu bar, then scroll to Still need help? and select Yes.
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