Using Outlook for iOS in business environments for email and scheduling
This email has been explained a multitude of times in this thread, if you'd have taken the time to read. It's spam. They use some email property manipulation to fake your email and make it appear as yours - it is NOT from your account. Just delete that email and move on.
The people claiming they have been hacked are entirely unrelated to this email. I'm not surprised that people who claim they have been hacked by this have actually been hacked, as they likely have used the same password for dozens of accounts on different services and have had them leaked with a data breach, much like any other account hijacking. That's the same reason for seeing your email being attempted to be logged into 1,000's of times when you view your account activity.
It simply means your email address has been exposed in a data leak and bots are trying to check your email for a correct password. Just keep your password separate from other services and you won't have to worry about any of this. Secondly, don't click dodgy links and do not give anyone your information. Double-check your URLs before you try to login anywhere. Very basic practices.