There really is a sweepstakes, and there really is a lot of suspicion about it. This is because all you need to do is fall for the marketing once, and Microsoft spam you about it every single week. Worse, they don't even provide an opt-out link.
Many countries have rules against this kind of spam, so I encourage users to check the laws in their jurisdiction and see if they can make a complaint. In the UK I complained to the ICO for example. The most fundamental rule where I live is this:
"You must not disguise or conceal your identity, and you must provide a valid contact address so they can opt out or unsubscribe."
https://ico.org.uk/for-organisations/direct-marketing-and-privacy-and-electronic-communications/guide-to-pecr/electronic-and-telephone-marketing/electronic-mail-marketing/
So this morning, I filed a complaint using this form:
https://ico.org.uk/make-a-complaint/nuisance-calls-and-messages/spam-emails/report-spam-emails/