Unfortunately, spam and scan e-mails are common, and there is no way to prevent them. What you can do is implement ways to protect yourself, and education yourself as to the risks on the internet. The good news is, you're already using Firefox, which is a great way to keep yourself safe on the internet. Here are some other ways to keep yourself safe:

• I strongly suggest uninstalling any Anti-virus on your computer (like McAfee, Norton, etc.) and just use the built in Windows Defender. Then, go to www.malwarebytes.com, and download malwarebytes (for free) and run it once a month.
• Also, you should do a few things to further protect Firefox. Install https://addons.mozilla.org/firefox/addon/ublock-origin/ to block ads on the internet.
• I'd also suggest enabling Tracking Protection, What happened to Tracking Protection? to block websites from tracking you around the web.
• Finally, make sure you always install all Windows updates.

Here's a good article on how to identify spam e-mails. https://www.wikihow.com/Recognize-Spam

Thanks Tyler, Will be following your advice.

Just by the by; I was in about 1st or 2nd year at high school (Zimbabwe - Rhodesia back in the day) when after assembly the maths teacher addressed us and held up a calculator (plastic brain). It was the very first time I saw one and was amazed!?!

Greg.