Adobe Acrobat Pro X - Attach file to Email Not Working

Good Morning, 

One of the customers I support is having an issue attaching files to email within Adobe Acrobat Pro X.   When they select the option to Attach a PDF file, they get the following message.   

Specs: 

Windows 10 64-bit 

Microsoft Outlook 2016 ( a part of Office 2016)

Adobe Acrobat Pro X

So far, I've set the default mail application in Windows 10 to Outlook 2016, but that did not fix the issue.  Through my reading of various forums, I've seen some suggestions about changing some email settings in Acrobat Pro, but I don't see any available in the version we're using.  

Are there any solutions for this issue?