In my experience American Express will not use conventional email, but there is a Secure Message Center on the website. Login > Summary of Accounts > See More > Check or Send Messages About Your Account. They will send you an email to tell you when a reply has been posted.
dennis
The Secure Message Centre is a good idea but not when they set an expectation of a response within 24 hours and 60 hours on they still haven't delivered...not even so much as a holding statement. Poor show yet again.