Oh crap, brainium overloadicus. Must be time for a nap now. LOLOLOLLet's not forget the OP is merely asking for help. No idea his computer knowledge and it's not relevant.
FWIW: the general public really has no idea what an infection vector emails are let alone the Non-Stop SPAM from a public email address. I don't know why the email didn't work but I suggest it would have been blasted to useless by non-stop SPAM email flooding the inbox.
Any and all virus scanners didn't find anything. HAHAHA Isn't that cute! But frankly it's not the final answer. Maybe one has a new bug/virus/malware/adware that the scanners don't know about yet. Submission of the unwanted undetected program can get interesting. Banner ad or pop-up ad malware that got installed via a drive by download ... Too technical.
Say a unwanted as display program gets on your computer and is unreliable, but, is new and gets past all virus scanners. It wants to serve an ad biased of whatever website you are on, but, crashes the computer instead. This is but one possibility.
Another is the virus scanner putting a whammy on the bad program and getting it's ass kicked by the bad program resulting in a PC reboot.
I have suggested hardware failure and may other things can come together in the perfect alignment of the moon and stars to crash a PC. Drivers, firmware, bad patches from Microsoft is a non-stop constant migraine nightmare called Black Tuesday...