Managing personal Outlook.com account settings, security, and privacy
Greetings!
This is Tin, I understand that you would like to remove the email address options, such as your ex’s account, that appear when you try to sign in to your apps. I'll do my best to help. May I know if it's happening in all of your apps or just a browser?
Please let me know on what exact application are you trying to sign in so I could share the steps that you can perform. Since it actually depends where are you seeing it. Is it on MS Edge? Google Chrome?
Will wait for your response.
Thanks,
Tin