Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello
What's your definition of association? If you mean using your email as username, it can only be one, Microsoft wouldn't allow using the same email address to sign up for another account.
If you mean using your email address as security contact info to receive 2FA code, then it can be used on more than one account. Use this method to look them up: https://support.microsoft.com/en-us/account-billing/forgotten-your-microsoft-account-username-b2049472-3b8f-27d3-61c6-67a668453f4c