I've installed an Exchange 2016 server with a lot of mailboxes. Now i'm migrating the emails from the old server to Exchange. So, create .mbox file, convert to PST and then import PST.
I don't know why or when duplicates are created.
I've done also this test with OWA:
- Select an email (suppose Message-ID: <firstname.lastname@example.org>) and copy this email on "Archive Mailbox";
- Move the same email to the same "Archive Mailbox";
In the normal folder now i haven't the email but in the "Archive Mailbox" i've the same mail twice with the same Message-ID header. The system as allowed this duplicate
How can i delete in a simple way all the duplicated emails (same Message-ID) leaving only one from OWA, Outlook2007/2010 or Exchange Shell? I've some mailbox with 20000 emails and more of them are duplicates