Sending, receiving, and organizing email in Outlook.com
If you haven't already, first, please check whether the missing emails are in "Deleted Items", "Archive", or "Junk Email".
If they are not in "Deleted Items", open that folder and select "Recover items deleted from this folder" at the top. Outlook.com may still allow the messages to be restored from there.
Microsoft's recovery steps are here:
https://support.microsoft.com/en-us/outlook/mail/recover-and-restore-deleted-items-in-outlook
Also go to Settings > Mail > Rules and check whether there is any rule you do not recognize that is deleting or moving messages. Check the "Filter" above the Inbox as well and make sure it is set to "All".
If the issue still persists, to help narrow down the issue:
- Are the disappearing emails showing up in "Deleted Items", "Archive", or another folder?
- Do you see any rule under Settings > Mail > Rules that you did not create?
Click "Add comment" to let me know.
Thanks!