Emails Purged From Outlook May Still Exist
After an email is deleted from the Deleted Items folder, or removed from the Inbox with SHIFT + DELETE, the email will be sent to the Deletions subfolder of the Recoverable Items Folder. The Recoverable Items Folder is not visible to the user. Each user's profile contains a deleted item retention period set by the admin. The default is 14 days. So, in most cases emails can be recovered for up to 14 days after a user has tried to delete them. The 'Recover Deleted Items' command is on the Folder tab of Outlook.
If an email is purged from the Recovered Deleted Items folder, or if the set retention period elapses, it is sent to the Purges subfolder of the Recoverable Items Folder. However, the email will not be removed from the Purges folder until the mailbox assistant processes the folder. A post on Microsoft's official site for Exchange states that: "You can configure the Managed Folder Assistant to process all mailboxes on a Mailbox server within a certain period (known as a work cycle). The work cycle is set to one day by default."