Hi @K W,
Thank you for posting your question in the Microsoft Q&A forum.
Regarding that you receive saying " User verification code for Microsoft Authentication.". I’d like to gather a few details to better understand your situation and assist you effectively:
In the current time please avoid clicking on any suspicious link on that email.
Have check who is the sender? You could open the mail header then put it in the message header analyzer to check who is the sender.
Or you could provide me the message header I could check it for you. To obtain the message header follow the step by step below
Right click on that mail then choose view and select view message detail.

After that copy the message detail and paste it in the message header analyzer or you could send it to me in the private message so that I could check it for you.

If you check the message header and the sender is not Microsoft please report
Please refer to this article for step by step to report : Phishing and suspicious behavior in Outlook - Microsoft Support
Refer to this article to know if the email address is from Microsoft or not (But if you are unsure please send me the message header via private message so I could check it for you) : Can I trust email from the Microsoft account team? - Microsoft Support
But if you want to block the sender right click on that email and select "Block" then choose "Block sender"

Thank you again for your time and understanding. While my initial response may not resolve the issue immediately, I’d like to gather more details about your situation so I can assist you more effectively.
I really appreciate your patience, and I’m here to help. Looking forward to your response!
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