Migrate from Outlook 2010 to Outlook 2013 on O365 without redownloading all mail


I am setting up users on new pc's. They currently run on Oulook 2010 with O365 and are moving to a NEW pc with Outlook 2013. The current mail runs through Office365. I would like to not have to re-download all the mail onto the new machine as some of the users mailboxes are very large. What is the process to move the mailbox from the one pc to the other and get the mail server not duplicate the mail. If i do an export and import onto the new machine i end up with duplicate mail (even though option to not import duplicates is selected) and this is because the mailbox on the new machine is empty and the mail server does not see the imported mail.

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David Johnson, CD, MVPOwnerCommented:
Outlook / Exchange uses .ost files which the user in cached mode can tell how much to download
Account Settings and the .ost file is considerably smaller than the mailbox.
sentinelsystemsAuthor Commented:
thanks, that is an option i didn't consider but is there anyway to have everything available offline as i know to get around this when staying on the same version of Outlook we just copy over the ost file and replace the one created on the machine once you have setup the account. Then all mail is available as it was offline and you don't end up re-downloading the mail or importing and ending up with duplicate mail.
Mark GalvinManaging Director / Principal ConsultantCommented:

You can configure those settings by GPO https://technet.microsoft.com/en-us/library/cc179175.aspx?f=255&MSPPError=-2147217396 


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sentinelsystemsAuthor Commented:
this is what i was looking for so as to simply replace the newly created OST file and NOT have to download all the mail again as the client wants ALL mail available offline.

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