Hi Lainie57,
Greetings. This is Alan Wu from Office 365 forum support and I am happy to assist you for your case here. Please be noted that I have covered the domain in your post for protecting the privacy.
For your case, my understanding is that the emails should not be sent by Microsoft as I have checked the domain and found it is not a Microsoft one. On another hand, it might be some phishing email or spam email. So, my suggestion is not to click any link in the email or type your password in for avoiding the attack. And, you can try blocking the sender so that you won't receive these emails. For more information, you can refer to
https://support.office.com/en-us/article/block-or-allow-junk-email-settings-48c9f6f7-2309-4f95-9a4d-de987e880e46 (blocked sender in Outlook Web App) Or https://support.office.com/en-us/article/block-a-mail-sender-b29fd867-cac9-40d8-aed1-659e06a706e4 (blocked sender in Outlook).
Regards,
Alan