Outlook handler won't install

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Outlook

Firts of all thanks for the fantastic Todolist, I've been using it for years, wouldn't know to do my work without it.

I recently discovered that I can link directly to outlook emails from todolist, but the functionality doesn't seem to works due to a missing handler. I get the following message:

[Window Title]
ToDoList 6.8.10 Feature Release

[Content]
ToDoList has detected that the handler for the 'outlook:' protocol
has not been installed.

Until the handler is installed, 'outlook:' links will not work correctly.

Do you want to install the handler now?

[Yes] [No]

When I click Yes, nothing seems to happen. Any ideas why and how to solve this?