The threat from 2 GB limitation remains a major challenge before the MS Outlook user. For preventing the files from exceeding the 2 GB limitation it is necessary to crop the PST files and remove duplicate emails on timely basis. Duplicate emails is another reason for the increase in size of Outlook files. To remove duplicate emails in Outlook should be the foremost priority of a user as they massively contribute in the size of PST files. A user can remove duplicate emails and significantly reduce the size of MS Outlook. Microsoft has not provided any separate utility for removing the duplicated files from MS Outlook so this has to be done manually only.

Steps to remove duplicate emails in MS Outlook (MS Outlook 2002, MS Outlook 2003, and MS Outlook 2007):

Open MS Outlook and place the cursor on Current View option (in View menu)
Open the Current View option.
Change the Folder View to Table Type View.
Note: The user would have to try a different method for MS Outlook 2003

Open Arrange By option in the View menu.
Select Current View for selecting the Table Type View from Folder View.
These details will be available there:
View Field
Calendar: Active Appointments
Contacts: Phone List
Inbox: Message List
Journal: Entry List
Notes: Notes List

By Right-clicking the header the Field Chooser option can be selected.
Now Go to Field Chooser options and select All fields.
Move the Modified field to table.

Note: Verify if the duplicate items have a different date from original items or not after that sort the items with the Modified option.

Determine the items that need to be deleted from the folders (Use the Shift Key for selecting the headers).
Delete the selected files with delete option.

Steps to remove duplicate emails in outlook (MS Outlook 2010):
Select the folders from where the duplicates are to be deleted.
View tab in Ribbon, click Change View for selecting the Folder View.
Right click the column heading and select Field Chooser.
Field Chooser option and select All field.
Move the Modified field to table heading.

Note: Verify if the duplicate items have a different date from original items or not, after that sort the items with the Modified option.

Determine the items that need to be deleted from the folders (Use the Shift Key for selecting the headers).
Delete the selected files with delete option.

This is a very lengthy method to remove duplicate emails from MS Outlook. For instantly deleting large number of duplicate emails, Kernel’s Remove Duplicate Emails tool can be used. This tool quickly classifies the duplicate emails in a tree like structure from where they can be deleted. It accurately deletes the duplicate files in two modes - Advance Mode and Standard Mode. It is highly compatible with all operating systems and supports all versions of MS Outlook.