Live.com login activity and a warning "Unusual activity detected"

I could not find a more direct forum than Outlook to ask this question, if it is not the right forum my apologies.

I received an e-mail alert that indicated unusual activity detected on my live.com account. When I checked the recent activity, I found two IP numbers. One matched my external IP and the other did not. I changed my password right away and checked the activity again. To my surprise, the other IP and its variants were appearing along with my external IP number at the same intervals.

I tried to find the IP number roots and ironically, it pointed at Microsoft. I am really confused! Can someone explain the source of this IP and whether I need to do anything to stop it from occurring.? I use Edge browser and I log in with my account. When it syncs, does it use a separate IP from my IP number?

Thank you,

Cemal

Note: I am not using the Outlook mail client. I check my mail using two different mail clients on two different computers at the same location that share the same external IP number. On occasion, I check my live.com e-mail online using a Web browser.