Outlook e-mail cannot Send after account compromise. How to re-enable Sending.

Hello! Can you check this article in here that shows all the points? https://learn.microsoft.com/en-us/defender-office-365/responding-to-a-compromised-email-account

Out of no where I got a pop up to show up on my computer the web page is: https://858b6l8x5gexi1.azureedge.net/gm/index.html?clickid=cs6ode55sqmc738op5pg It also gave me a number to call 1 (866)581-3515 being that is it is not a microsoft web site I never clicked on anything and I will not call the number. But can anyone tell me weather or not if this is a Microsoft security application or service for using MicroSoft products?