troubleshooting Question

OST Compatibility between Outlook 2007 and Outlook 2010, 2012 and later ?

Avatar of Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)Flag for United Kingdom of Great Britain and Northern Ireland asked on
OutlookMicrosoft OfficeOffice ProductivityEmail ClientsMicrosoft Applications
20 Comments2 Solutions552 ViewsLast Modified:
Hi Experts

Does anyone know for definitely the compatibility between OST files, are the standards the same between all versions of Outlook, e.g. 2007 and later 2010, 2013 etc going forward e.g. from 2007 to later, not backwards.

The reason I ask, is we have recently noticed that one of our users, has a offline mailbox size of just under 20GB, and this appears to be the maximum supported for Outlook 2007.

There is a reason we all have offline mailbox, whilst we have no remote access to Exchange, but didn't know there was a maximum limit in Outlook 2007.

So, if we were to upgrade from Outlook 2007 to a later version of office, and reconfigure and use the existing OST file, is it going to carry on as normal, or is it going to download all 20GB mailboxes again?

I'm trying to establish compatibility, and cannot find anything definitive from Microsoft.

We've tried compacting OST file, and despite removing many dead emails, over 20,000 it was made no difference to the sizes on the disks.
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