How do I make Lightroom CC recognise my default email application?

Hi, my first post so I hope in the right place.

I'm trying to email an image from within LR but the dialogue box shows my previous email client (Windows Live Mail) instead of the current one (Outlook 2016). Outlook is set as the default app in Start>Settings>Default Apps. I've tried adding Outlook manually in Email Account Manager, but although the email is sent, my image is embedded rather than being attached. My partner tried emailing for the first time and his Outlook was picked up immediately. What am I doing wrong?

Thanks.