Windows 10 Mail automatically downloaded a PDF attachment infected with a trojan virus from a phishing email. The file was saved onto my hard drive in LocalState user files where I later found other benign attachments collected. My current theory is that Mail caches all attachments this way but frustratingly It’s been hard to get a confirmation from support. I have found no option to disable this behaviour so far. This seems a huge and unnecessary security risk to me.

How can I prevent automatic email attachment downloads? 

Why is this on by default?

Will this option be reset the next time Windows 10 updates?

Why is support unfamiliar with this issue?