Assume that you deploy and integrate Microsoft Exchange Server 2016 (CU5 or CU6), Microsoft SharePoint Server 2016, and Microsoft Office Online Server on-premises for document collaboration experience. In this scenario, on-premises users can send OneDrive for Business (modern) attachments successfully. However, they experience an error when they try to view or download the modern attachments.
This issue occurs because the related dynamic link library (DLL) is missing.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.