In Outlook, Filters customize your view so that the emails you are looking at in any given folder are only those that adhere to the rules of the filter applied. For instance, if you search for email messages that contain the word Cat in the Subject field, the filter will only display email with the word Cat in the Subject field and hide all of the other messages from view. Outlook contains some commonly used filters under View > Current View and it is quite easy to turn those on accidentally, which could be the root of your problem.
If you have a filter that is not allowing all of the email in your Deleted Items folder to be displayed:
While you are in the Deleted Items folder click on View > Arrange By > Custom
When the Customize View window opens, click on the Filter button
When the Filter window opens, simply click on Clear All.
This will remove all of the filter criteria that had been set up on this mailbox, therefore all of the mail messages currently in the Deleted Items folder should appear. This is also the easiest way to remove multiple filters from a mailbox.
