Change your name or address
You'll find more similar links on this reference page:
http://www.apple.com/support/itunes/musicstore/
People with .Mac accounts CANNOT change their email addresses in iTunes. The field simply won't allow it. I have changed my email address in my Apple ID a long time ago and it has never updated in iTunes. It has updated for other services just fine. But NOT iTunes.
Dear Steve,
Thank you for contacting the iTunes Music Store.
We are working toward a resolution for the issue you have reported. Your
experience with the iTunes Music Store is of the utmost importance to us,
and we appreciate your patience as we strive to make it an enjoyable one.
Rest assured that we have flagged your request for follow up and will
contact you immediately once we have more information.
Sincerely,
iTunes Music Store Support
How do I change the iTunes receipt e-mail address?