"Administrator Change Restart Outlook" after uninstall of Exchange 2007 (now on Exchange 2013)

Question: After uninstalling Exchange 2007 (migrated to Exchange 2013) most users are getting a pop-up saying that the administrator has made a change requiring you to restart Outlook.  How do we get this to stop?

Backstory:We have recently upgraded from Exchange 2007 to Exchange 2013.  After about 6 weeks of having everyone moved to the 2013 server and removing all of our public folders, we decided it was time to uninstall 2007.  As a test, we had turned off the 2007 server for a week to make sure we didn't encounter any problems.  When I went to uninstall, I got error messages that the Public Folder database still existed, so I attempted to delete the public folder database from the EMC.  That gave me an error saying that the database was created in a newer version of Exchange.  Apparently that is a common issue when upgrading from 2007 to 2013.  The only advice that I found was to make sure all the public folders were gone from that database and then use ADSI Edit to remove the database.  I followed Microsoft's instructions for removing all the public folders, and it appeared that they all were removed except for "IPM_Subtree".  I was not able to find any information on what that folder was for or how to get rid of it.  Since we had gone a week with the server being off without problems, I went ahead and removed the Public Folder Database using ADSI Edit.

A couple of the IT staff noticed that new email was disappearing and reappearing every few seconds.  Removing cached mode and the re-adding cached mode fixed that issue.  Only four people in our organization of about 600 email users have reported this over the past two days.  Almost everyone is noticing the Outlook pop-up, but at different frequencies.  I notice it when I first open Outlook each morning, I click "OK" restart Outlook and don't see it again the rest of the day.  Others see it over and over again (as frequently as every few minutes) regardless of whether they restart Outlook or not.

We have tried upgrading to CU5, removing our Anti-virus (GFI Vipre) from a client machine.  Neither helped.  We have a feeling there is something still pointing at the old server (obviously), but not sure where to start.  Any help would be appreciated.

Thanks in advance.
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Not exactly the same pop, but may be …
After uninstalling and removing an Exchange 2007 not used anymore we had some issues with outlook. We solved the problem with update of some Entries for the autodicover services on DNS .  http://technet.microsoft.com/en-us/library/ff923256.aspx  on our case SSLOffload.
ejscnITAuthor Commented:
Hello all,

We resolved this issue by calling Microsoft.

There is a known issue when migrating from Exchange 2007 to 2013 that Public Folder Databases on 2007 cannot be removed using PowerShell or EMC.  We had to remove the public folder database using ADSI Edit.  This is what caused the issue.  The new databases still pointed to the Public Folder databases.  If you go into ADSI Edit and look here:  

CN=Configuration,DC=DOMAIN,DC=LOCAL  (you may have to right-click ADSIEdit in the left pane of the console and select the "Configuration" naming context to see this)
CN=Microsoft Exchange
CN=Administrative Groups
CN=Exchange Administrative Group (FYDIBOHF23SPDLT)

For each of our databases, we went into the properties and found the msExchHomePublicMDB.  What was in there was pointing at our old Public Folder database.  We cleared that and the problem was solved!  

I hope this helps someone else.

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ejscnITAuthor Commented:
Called Microsoft for support.
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