Outlook 2010 showing "Mailbox Full" warning when Exchange account is set to unlimited.

I have a user with Outlook 2010 that attaches to our Exchange 2013 server.  This user has a very large inbox.  I was importing a PST that is about 12.2GB when I noticed that there was a yellow messagebox under the toolbar in his Outlook that said "Mailbox Full   Your mailbox is full, you may not be able to send or receive items."

So I logged into ECP and changed everything under "Mailbox Usage" to be "unlimited".

Then I restarted his laptop and logged back into the network and opened Outlook 2010.  The message is still there.

Why is Outlook 2010 saying that the mailbox is full when Exchange 2013 says the mailbox is unlimited?

Also, why would Exchange report only 5.38 GB in his mailbox when his OST file is 12.2 GB?
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Will SzymkowskiSenior Solution ArchitectCommented:
Does this happen in OWA? use the get-mailboxstatistics -identity "username" | fl and check the "StorageLimitStatus" and if it is set to unlimited then it should be fine.

If it is Outlook i would create a new outlook profile to see if this corrects the behaviour.


As suggested, if there is no problem with OWA (or if the get-mailboxstatistics" shows that the mailbox has no no limit, the problem is on client side.
Disable cahed mode, remove the .ost file, and enable again the cache mode.

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