I tested to migrate several mailboxes from Exchange 2010 to Exchange 2013, but it's Dupulicates folder like calendar and contact.It seems known issue, but it's already CU6 even though it's written as below.
It's a lot of mailboxes that needs to migrated, so before migration, it should be avoided.
>This issue occurs because the EntryID property of the default folders is lost during the migration. Therefore, Exchange creates a new folder by using the same names.
To avoid folder duplication with future moves, install the following cumulative update, and then move the mailboxes:Cumulative Update 6 for Exchange Server 2013
Would you please share your information and resolution for this issue?