In Exchange there is one object with identity="sales". In addition, there are other objects with a different identity, but alias="sales". These are all delivered by "get-mailbox", which leads to duplicates in Identity Manager (1IM).
This is a product defect (32818).
This will be fixed in a future release of the product. If you require this immediately corrected, please contact Support for a hotfix referencing the defect ID 32818.