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"One of our users suddenly had this issue, this user had over 340.000 contacts most of them duplicates. As it turns out it was a syncing issue with his mobile phone. Deleting 340.000 contacts using Outlook is a painful task, so I figured out another way to do it. Here are the steps I took:\n\n\n\tDisabled the synchronization \n\tRestored the user' contacts from a recent back-up into a PST file. We are using Commvault software which has this option. You can also export the existing contacts using PowerShell.\n\tDeleted the contacts using PowerShell.\n\tMoved the contacts from the PST back into the users mailbox.\n\n\nStep 1, 2 and 4 are quite trivial, and I assume you know how to do that. The second task is a bit more complicated, and requires some special rights within your Exchange organization. The complete PowerShell command I used to delete only the contacts from the users mailbox:\n (more&hellip;)"
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