Earlier this week a user asked how to backup Outlook data without duplicates.
Normally, we tell users to copy their pst file to use as a back up as it have everything in it. However, this user was exporting his Exchange mailbox for backup.
Although backing up an Exchange mailbox to a pst file is not a good backup solution, I know it's the method more than a few users employ, usually because the administrator won't restore backups when a user needs to find a lost message.
For this scenario, a filtered export will work. I highly recommend using a Query Builder filter, looking for "In folder" to avoid exporting junk email and deleted items, in addition to overwriting or skipping duplicates. If you do this regularly, the filter can be set to export items modified since the date of your last export.
Unlike Archiving, which removes the old messages from the mailbox and does not include Contacts, exporting makes a copy of all items, including contacts. To include all folders, select the top of the mailbox and choose the option to include subfolders.
On the server side, the administrator could use the Export-Mailbox cmdlet to create backup pst files for users.
This cmdlet would export all content, except for the junk email and deleted items, to a pst file and check for duplicates:
Export-Mailbox -identity diane -AllowMerge -ExcludeFolders "\Junk E-mail","\Deleted Items" -PSTFolderPath C:\PSTFiles\diane.pst