Q: How can I make sure my Deleted Items folder is empty in Microsoft Outlook?

A: I had a user the other day who insisted his Deleted Items folder was empty, but his mailbox was still pushing against the company's mailbox size limit policy. I've seen users accidentally move content to unexpected places without realizing it. For example, in Outlook it's possible to drag and drop a mail folder into the Calendar, Contacts, Tasks, or even Notes folders. Or the content could still be in Deleted Items, even if it doesn't appear to be so to the user.

The person who assured me his Deleted Items folder was empty was actually selecting the Deleted Items folder in the Navigation pane, highlighting the content in the main pane, then deleting the highlighted content. This method works, although it's somewhat tedious, but it misses content that might have been deleted from within subfolders. When you delete a folder, its contents are moved to Deleted Items as a subfolder. The contents of the subfolder aren't visible in Deleted Items unless the subfolder is selected in the Navigation pane. Also, when you select Deleted Items, it doesn't show the folders in the main pane; you have to click the little plus symbol (+) or arrow beside Deleted Items in the Navigation pane for those folders to appear, as Figure 1 shows.

Figure 1: Expanding Deleted Items in Outlook to show deleted subfolders (Click image for larger view)

To delete these folders, you have to either do so one at a time, manually (not a good idea), or use the more logical Empty "Deleted Items" Folder or Empty Folder option from the right-click menu on the Deleted Items folder. You can also use the Empty Folder button on the Folder tab of the Ribbon in Outlook 2010 or go to Tools, Empty "Deleted Items" Folder in Outlook 2007 or Outlook 2003.

In addition, Outlook makes it easy to view the size of folders within the hierarchy so that you can identify where the greatest mailbox volume resides. You can right-click the account in the Navigation pane and select Data File Properties (or Properties) from the bottom of the context menu. On the General tab of the Properties dialogue box, click the button for Folder Size to open a window listing individual mailbox folder sizes in KB. Figure 2 shows an example with a small amount residing in Deleted Items. Unfortunately, this window isn't resizable, so if you have many folders, you'll have to scroll through them to see the full list.

Figure 2: Viewing actual folder sizes in Microsoft Outlook

Although the user I was working with claimed the Deleted Items folder was emptied, I was able to use this method to find a large amount of content still in that folder. Exchange administrators can also access this information without using the Outlook client, of course, by using Exchange Management Shell (EMS) and the Get-MailboxFolderStatistics cmdlet.