Unable to send from Adobe Acrobat. Default email application greyed out

Environment:
Windows 10
Outlook 2016
Acrobat XI Standard

Issue:
Unable to attach PDF from Acrobat using Send option. Default email application is greyed out.

Fix:
Make sure Outlook 2016 is set as the default program for mail.
This should remove the greyed out option, and bring you to issue number 2:

There is no email program associated to perform the requested action.

Fix:

1. Click Start, and then click Run.
2. In the Open box, type regedit, and then press ENTER.
3. In Registry Editor, locate the following subkey in the registry: HKEY_LOCAL_MACHINE\Software\Clients\Mail\Microsoft Outlook
4. Select the subkey, and then press DELETE.
5. Click Yes.
6. Quit Registry Editor. 
7. Go to programs and features, repair office 2016