Hi @Talha ,
Did the user import any .pst file to your mailbox before? As I know, it may cause some duplicate emails if we import a file and forget to choose "don't import duplicate". And agree with michev, we could first try to log into your web mail to check if there are any duplicate items there.
Also, for your requirement of removing duplicate in Outlook, I found a relevant VBA script below. Accoridng to my tests, it could remove the duplicate items that I copy and paste manually in a specific folder, so please try to press "Alt + F11" to paste the script and run it in the user's Outlook to check if it could also work for you (Notice: we may need to Enable all macro in Outlook to run the script--File>Option>Trust center>Trust center settings>Macro settings>Enable all macro) :
Sub DeleteDuplicateEmailsInSelectedFolder()
Dim i As Long
Dim n As Long
Dim Message As String
Dim Items As Object
Dim AppOL As Object
Dim NS As Object
Dim Folder As Object
Set Items = CreateObject("Scripting.Dictionary")
'Initialize and instance of Outlook
Set AppOL = CreateObject("Outlook.Application")
'Get the MAPI Name Space
Set NS = AppOL.GetNamespace("MAPI")
'Allow the user to select a folder in Outlook
Set Folder = NS.PickFolder
'Get the count of the number of emails in the folder
n = Folder.Items.Count
'Check each email starting from the last and working backwards to 1
'Loop backwards to ensure that the deleting of the emails does not interfere with subsequent items in the loop
For i = n To 1 Step -1
On Error Resume Next
'Load the matching criteria to a variable
'This is setup to use the Sunject and Body, additional criteria could be added if desired
Message = Folder.Items(i).Subject & "|" & Folder.Items(i).Body
'Check a dictionary variable for a match
If Items.Exists(Message) = True Then
'If the item has previously been added then delete this duplicate
Folder.Items(i).Delete
Else
'In the item has not been added then add it now so subsequent matches will be deleted
Items.Add Message, True
End If
Next i
ExitSub:
'Release the object variables from memory
Set Folder = Nothing
Set NS = Nothing
Set AppOL = Nothing
End Sub
Hope that would be helpful to you.
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