BR,
Christian

If that was the case, how comes the users had missing items?

Importing into empty mailboxes should not miss items.

Sorry to question you but I do not understand and hope you don't mind

many thanks,
Paul B.

The PST's was imported to empty mailboxes.
When the PST's that contained duplicate Items was imported without -AllowDuplicates, only one Item would be imported, and this would be the Item with the latest modified time. When importing without -AllowDuplicates, every Item is checked against the Items in the mailbox. If a duplicate is found, the Item with the last modified time will "win". No Items are deleted from the PST's.

BR,
Christian

Please could I ask you about your experience with the -AllowDuplicates switch.

Typically when you move service provider, the user has an empty mailbox, if you imported the PST file into an empty mailbox there would be no duplicate items unless they already existed in the PST file.

If they did exist in the PST file prior to importing, are you saying that the Import-Mailbox Cmdlet found a duplicate item in the PST file and did not import the item at all?

I would of expected that WITHOUT the -AllowDuplicates switch, if an item already existed in the mailbox, the Import-Mailbox Cmdlet would not have imported the duplicate item.

You are saying that after you imported a PST file, a user was then missing items.

Are you saying that the Import-Mailbox Cmdlet WITHOUT the -AllowDuplicates switch, found an item in the mailbox, decided not to import the duplicate item and also remove the original item from the mailbox?

many thanks,
Paul B.