The Microsoft Exchange Mailbox Assistants service (MSExchangeMailboxAssistants.exe) crashes after the mailboxes are migrated from an Exchange Server 2007 server to an Exchange Server 2010 server. Additionally, the following event is logged in the Application log:
This issue occurs because the Microsoft Exchange Mailbox Assistants service does not catch the StoragePermanentException exception that is caused by the IncorrectValueType error. The error occurs when the service tries to stamp the BodyTag property of message items after the mailboxes are migrated.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.