Public folder database migration issue in a mixed Exchange Server environment

It takes a long time for the migration of public folder data from a single public folder database into multiple public folder mailboxes. This issue occurs in one of the following mixed environments:

• Mixed environment of Microsoft Exchange Server 2007 and Microsoft Exchange Server 2013
• Mixed environment of Microsoft Exchange Server 2010 and Exchange Server 2013
• Mixed environment of Exchange Server 2007, Exchange Server 2010, and Exchange Server 2013

Additionally, when this issue occurs, you receive one or more of the following error messages.
If the environment has Exchange Server 2007 as the source server, you receive an error message that resembles the following:
If the environment has Exchange Server 2010 as the source server, you receive an error message that resembles the following:

This issue occurs because Exchange only allows a single migration process to log into the public folder database at a time. It causes data migration to all the target mailboxes to be done one at a time.

To resolve this issue, install the update rollup that is dated November 2014:

• Get the Update Rollup 15 for Exchange Server 2007 Service Pack 3
  (http://support.microsoft.com/kb/2996150)
  .
• Get the Update Rollup 8 for Exchange Server 2010 Service Pack 3
  (http://support.microsoft.com/kb/2986475)
  .

After you apply this update, Exchange is updated to let multiple migration processes log into the source public folder database immediately. This allows data migration to all the target mailboxes to be done in parallel. Load limiting will still apply, so you will not see all migration tasks working all at the same time.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.