Unknown other account/profile where "that email address already associated with another XB ...

I have the exact same problem.... except that I bought my Xbox 360 used and don't know the family settings pass code so I'm trying to go through the Microsoft/Xbox website to try and get an answer as to how to reset that pass code, and have no help. Seems
to me that the only help available is for Xbox One. Can you please let me know if you have any breakthrough on this issue

To WPAK , the money shouldn't be an issue , you are informed before the swap that money will not transfer . As for the " non MS account email " , I've seen something similar to that but can't remember where , & other than Apple email I don't of any other
service . Each profile can only have one email account associated to it ; I have 2 profiles , one with a working email address & the problem profile with the outdated ( but verified ) address . When I first attempted the swap I tried to use the working address
from the other profile & was told I needed another account not associated with a profile . I made another email account but it's not working . The accounts I'm working with are cox.net ( the expired one , associated with #1 profile ) , gmail.com ( associated
with #2 profile ) , & outlook.com ( the address I want to swap to profile #1 ) . Profile #1 has all of the achievements that took me years to get , profile #2 is secondary , for my little nephews to use when they're visiting . I've gone to a MS support service
& asked about swapping out alias's in my cox.net account ( & then deleting cox , making outlook the primary )& how that would effect my profile . Waiting for an answer , will post it here when I get it .

Hi Richard_Bedford. My name is Kyle and I'm an independent advisor.

Keep in mind that you're adding it to your Microsoft account, not your Xbox profile. An Outlook email is already associated with a Microsoft account when it's created, so it cannot be added to another account. That is why you receive the 'email address is already taken. ' error. In this case, you'd have to use a different email that isn't already associated with another account.

Please reach back if you have further questions.

Thanks,
Kyle

Hello,

It means you already have a Xbox Account associated to your Email you put in for your new account. Try using another email. Or change the email address of the account associated with the Email you are trying to use.

Hi Nick_674

A gamertag is linked to a Microsoft account. You can create a new account and associate a new gamertag with it, but all accounts must have a unique email address. This email address can be an existing address, but it can't already be associated with another
account.

To recap... one email address = one gamertag. But you don't need to create a new email address.

Hope that helps.