HINTS TO HELP YOU.
I see new emails coming in but after some seconds they are automatically remove themselves from my mailbox. I don’t have any rules configured that would move or delete these items.
How can I get this to stop and get to those messages?



There are 3 common scenarios in which this could happen.
Unread Messages filter
If you are looking at your mailbox via a filtered view or via the Unread Mail Search Folder and also have the option configured to automatically mark emails as read after x seconds, then it could happen that the messages automatically disappear when they get marked as read.
Read More -
Messages automatically disappear after receiving | MSOutlook.info