Sending, receiving, and organizing email in Outlook.com
To determine if the email you received is genuinely from Microsoft, you should check the sender's email address. Microsoft support typically uses domains such as microsoft.com, microsoftsupport.com, or mail.support.microsoft.com. If the email is from a different domain, it is likely a phishing attempt.
In your case, since you received a notification about unusual login activity, it is crucial to verify the sender's email address and be cautious. Do not click on any links or provide personal information until you confirm the legitimacy of the email. You can also report the email as a phishing attempt if you suspect it is fraudulent.
For further guidance on identifying phishing emails and reporting them, you can refer to Microsoft's resources on protecting yourself from phishing scams.