Your email address is linked with the Siemens ID login procedure. If you have to change your email address, you have to create a new Siemens ID login with your email and a password. You have to register again with your new email login data.
If you have important data (e.g. products in watchlist, product offers, service inquiries, etc.) you need to go in contact with the LDA Portal helpcenter via the 'Contact us'