Messages automatically disappear after receiving

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.

If you are in an (Unread Mail) Search Folder, switch back to the normal Inbox folder and see if your items are there.

If you are in the Inbox folder already, make sure your view is not set to “Unread Messages in This Folder” or that you have a filter applied to your view.
To change or reset your view use;

• Outlook 2003
  Change view; View-> Arrange By-> Current View-> Messages
  Reset view; View-> Arrange By-> Custom…-> button Reset Current View
• Outlook 2007
  Change view; View-> Current View-> Messages
  Reset view; View-> Current View-> Customize Current View…-> button Reset Current View
• Outlook 2010
  Change view; tab View-> button Change View-> Compact (and optionally set the Arrangement to Date)
  Reset view; tab View-> button Reset View

Default delivery location for an Exchange mailbox is set to a pst-file
If you are using an Exchange mailbox, make sure you don’t have the default delivery location set to a pst-file. When this is the case, all items that are being received via your Exchange account are moved out of the inbox and into the pst-file.

To verify/change your default delivery location;

• Outlook 2003
  Tools-> Account Settings…-> button Next-> use the drop down list at the bottom to set your default delivery location
• Outlook 2007
  File-> Data File Management…-> select the Exchange mailbox-> button Set As Default
• Outlook 2010
  File-> section Info-> button Accounts Settings-> Account Settings…-> tab Data Files-> select the Exchange mailbox-> button Set As Default
  Additionally, on the E-mail tab, select the Exchange account and verify that your delivery location is set to the correct mailbox.

Third party add-ins
The automatic moving of items can also be caused by any add-ins that you have installed. Depending on the method that they use, they might appear in the Inbox first and are then directly taken out of it. The most common add-ins that do this are virus scanner and anti-spam filters that integrate with Outlook.

If you have such an add-in installed, you should check their settings to see what they do with the emails; move it to another folder, delete it directly or move it to some storage/quarantine location of their own. You can consult the vendor of the add-in which options are available to you.

When you have a virus scanner installed which integrates itself with Outlook, you can safely uninstall this component of your virus scanner as it doesn’t add an extra level of safety and can lead to other send/receive issues as well.