Post migration you might start having issues with mobile devices using ActiveSync not synchronising correctly with Exchange Server 2010. It might work for a couple of days and then stop working. During this time users don’t receive any email to their mobile devices, but they can send email.
You might also get an error on the iPhone Cannot Get Mail, The connection to the server failed.
You might be using Quest Migration Manager for Exchange v8.7, and in the mail source and target agent logs you might see entries similar to this.
Source log:
5/27/2011 10:01:55 AM MailKernel::ExportSource Informational 2049 Current ‘\ExchangeSyncData\AirSync-iPad-ApplDLXFLPQ3DFJ3\32’ (Server: ‘DC-EX-SYD’, SourceKey: ‘E61D05A5193EBC45AD744414926F0CAA00207BF29745’).
Target log:
27/05/2011 8:39:10 AM MailKernel::ImportTarget Informational 2049 Current ‘\ExchangeSyncData\AirSync-iPad-ApplDLXFLPQ3DFJ3\32’ (Server: ‘DC-AU-EX-01’, SourceKey: ‘E61D05A5193EBC45AD744414926F0CAA00207BF29745’).
What is happening here is Quest Migration Manager for Exchange is synchronising the ExchangeSyncData folder from the source mailbox to the target mailbox. The entries are not needed on the target as fresh new sync partnerships will be be created by the mobile device.
Download an application called MFCMAPI from http://mfcmapi.codeplex.com/ and use this to connect to the user’s mailbox having the problem.
- Get the user to delete the mail account from their mobile device
- Open MFCMAPI > click Session > Logon and display store table
- Create a new profile and add the user’s mailbox
- Expand ExchangeSyncData and delete all the folders that exist under here.
- Get the user to re-create their mail account on their mobile device.
Marc Kean 
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SUCH a wonderful and ever so thankful post. Saved many hours – knew about MFCMAPI before, just didn’t know the device(s) on which one to delete. Used Exchange Console to attempt remove mobile device, wrote down the 2 giving me fits (1 old Ipad, and 1 Old Iphone) and used mfcmapi to user’s mailbox and removed the devices – also found some 6 year old Good Mobile Messaging data still tied to the mailbox. A VERY cool tool.
I have tried to use this program to remove a corrupt activesync device. I get root mail box instead of root container. I read that you need to set up outlook to not used cached mode. I logged into my computer with the credentials of the affected user after giving him local admin rights. I set up outlook to my exchange server and unchecked the cached mode box. I still get root mailbox instead of root container. Does it matter that the user may be using outlook from his PC at the same time? Please advise.