PST is not a outlook data file error

Hi,

I have used Outlook 2013 to export IMAP emails from Gmail account, and I have successfully exported each month of email into separate PST files so that I can move these PST files over to another computer.

I need to import these PST files into Outlook 2010. But some PST files are showing error message as below. I can import these pst files back into Outlook 2013 and they work fine but when they are moved to Outlook 2010 some PST files show the error message.

The reason I need to import these into Outlook 2010 is that we are in the process of migrating gmail to Exchange. I also need to make all email as PST files so they can be stored in a file server where computers can import them into their outlook whenever they need.