Email and Password saved to Safari Passkey not updated.

Problem Description:

I have changed the email associated with my Apple ID, but my old email is no longer accessible for personal reasons. Recently, when I used Safari to log in to idmsa.apple.com, which is the login page for Apple ID, the “AutoFill” function displayed my old email and showed it in the “Passwords” section. Through research, I learned that Apple distinguishes between “Passwords” and “Passkeys” as two separate security models, and it seems that “Passkeys” cannot be deleted manually. Additionally, I did not find this “Passkey” under my “Passwords” list.

Solutions I’ve Attempted:

1. On my MacBook, I used Terminal and ran the “security” command to delete all content related to my old email.

2. I opened “Keychain Access” and deleted all entries related to idmsa.apple.com or apple.com logins.

Both methods failed to resolve the issue; iCloud Keychain still prompts my old email address, causing an error. Additionally, I noticed that this “AutoFill” issue only occurs when using Safari to log in to my Apple ID. When I use Google Chrome, I don’t encounter this problem. I also tried turning off “AutoFill” and manually entering my old email to log into my Apple ID, and I was still able to access the account settings page. However, since my linked email has been changed, this old email can no longer receive verification codes.

Question:

How can I delete the prompt that displays my old email when logging into my Apple ID? Specifically, the “Passkey” for idmsa.apple.com that still shows my old email. Is this issue related to iCloud synchronization?

[Re-Titled By Moderator]