How will I know if someone else has access to my account, I have checked on my account security details there is no email that's not mine but when I want to reset my password there Is a email I don't know as a option

Question

I can sign into my account from Microsoft and it accepts my password when I change it but on my authenticator app and on the Xbox app even if I reset my password it tells me that my password is incorrect and there is a option to send a email code to some @mcmfa.ei