ERROR: "Either there is no default mail client or the current mail client cannot fulfill the messaging request"

Behavior:
When attempting to send a document from DocuWare, you receive the error 

"Either there is no default mail client, or the current mail client cannot fulfill the messaging request"

Outlook is already set to your default mail client, but the error persists.

Solution:
This is due to an issue with a registry file; repairing Outlook will not be enough.

You'll need to do a complete uninstall of Outlook and then install it onto your PC again, as well as a reinstall of all DocuWare Desktop Apps.
Once the above has been done, the error will no longer appear, and sending a document from DocuWare should work as intended.

KBA is applicable for both Cloud and On-premise Organizations.