Symptoms
Assume that you use Microsoft SQL Server 2016 Reporting Service to create a subscription, and you configure it to generate a report as a PDF attachment. After the subscription is run, you receive the email attachment. However, you the attachment is not recognized as a PDF file by some email clients.
Cause
This issue occurs in Reporting Service 2016 because the MIME content type inside the email message is set to the Application/Octet-Stream type instead of the Application/Pdf type.
Resolution
This fix for this problem is included in Cumulative Update 3 for SQL Server 2016 Service Pack 1.
Each new build for SQL Server 2016 contains all the hotfixes and all the security fixes that were included with the previous build. We recommend that you install the latest build for SQL Server 2016.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology Microsoft uses to describe software updates.