If you are referring to the email address that is associated with the support.okta.com portal, this email is associated with your super admin user account. If you update the super admin account with the email address you would like to use, new help requests should go to that email address. However, if you are referring to updating the End User Support email address, log into Okta as administrator Setting Account End User Support (click Edit) update the Technical Contact info. If you have additional questions please do not hesitate to open a support case.
Thank you, Ruchir Parikh Technical Support Engineer