Outlook 2013: Imported or copied items from .pst file disappear after a few seconds

Question

I am migrating from an open source email platform (Axigen) to Outlook/Exchange 2013. The Axigen system uses a connector for Outlook allowing users to use Outlook as a client.
To move from Outlook 2010 with the Axigen server to Outlook 2013 with Exchange I have exported the entire mailbox from Outlook 2010 to a .pst file which I am then trying to import into Outlook 2013.
The import process appears to complete successfully and the imported items show up in Outlook 2013 - but only for a second or two. Then they disappear completely, nowhere to be found. This happens with  ontacts, emails and calendar items and the result
is the same whether I import the entire mailbox or just a folder at a time.
If I OPEN the .pst file into Outlook 2013 everything in it looks perfectly OK, I can view items with no problems, all folders are there with their correct content. Now if I try to move or copy
items from the opened .pst file into the Outlook 2013 mailbox, I get the exact same symptoms as when importing. Items show for a couple of seconds and then disappear. If I copy or move a
folder, the folder remains in the Outlook 2013 folder tree but the items in it disappear.
Why would items be perfectly visible and readable from an opened .pst file but disappear when they are copied into the new 2013 mailbox?
They are not visible in OWA either, btw, so this is not just Outlook not displaying them, they are really gone. Checking the folder size in Outlook shows an empty folder (size 0, 0 messages). I have tried the /cleanviews switch when starting Outlook.
This has me completely stumped. Any ideas?
Thanks in advance!

Answer 1

More strangeness:
I set up an Android phone to sync with this account just now. I imported my contacts list from the phone into the Exchange account. After sync, all the contacts are perfectly visible on the phone, but NOT in Outlook 2013 or in OWA...
So maybe it is some sort of display filter thing after all? 
That's unbelieveable that message is visiable in Android phone through Exchange ActiveSync but cannot be viewd in OWA...
For the database session, we may enable
Exchange Mailbox Audit logging(http://technet.microsoft.com/en-us/library/ff461937(v=exchg.150).aspx) to check if the message is indeed upload into DB from Outlook.
For the client level, please enable Outlook logging to log what happens inside outlook to aid in your troubleshooting.
We can enable Outlook logging in Outlook 2013 under File > Options > Advanced > "Other" section
Log files are created as .etl files and stored in %userprofile%\Local Settings\Temp.  A new log file is created each time Outlook starts.
Cheers,
Tony Chen
Forum Support
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Okay, I have enabled Outlook logging. However I cannot find any way to read those .etl files.
I also enabled audit logging in Exchange but as I understand it that will not log operations performed by the mailbox owner, only non-owner access. 
I think I am close to giving up on this. I can't believe an enterprise email platform will simply delete messages copied into a mailbox without any error message whatsoever, and no way for an admin to track what is happening.
It is definitely happening when syncing with Exchange, so there must be something in these items (and
remember this happens not only to email messages, but also to Contacts) that makes the Exchange server decide these messages should be discarded witout warning.
One other thing: Folders copied from the .pst are visible on Outlook (although their contents are deleted) but not on ActiveSync clients. If I create a new folder in the mailbox, it syncs as it should.