How do I update the email address for my Apple card

Hi, you can update/change your email address and other information pertaining to your Apple Card. Here is a support article on how to update your email, including personal information,

How to change your Apple ID to a different email address

Go to appleid.apple.com and sign in.

In the Account section, choose Edit.

Choose Change Apple ID.

Enter the email address that you want to use. 

Choose Continue.

If you changed your Apple ID to a third-party email address, check your email for a verification code, then enter the code. Learn what to do if you didn't get the email.

If you use services like iCloud or Messages to share with friends and colleagues, sign in to those services with your updated Apple ID.

https://support.apple.com/en-us/HT202667

https://support.apple.com/en-us/HT209228

I hope this helps.