When registering with Fotoware you use your email address and a password to identify yourself so that you can log on to the Fotoware Customer Portal and get access to licenses and software. If you get a new email address, you need to update your information with Fotoware.
The email address cannot be changed per se, so you need to create a new account with Fotoware based on your new email address. When logging on to the customer portal with the new email address and password, register your Agreement or individual licenses again, and you're all set.
If you like, you can contact your local Fotoware Partner or get in touch with Fotoware Sales directly to have them remove the old email account from the system so that it is no longer connected to your company's agreement.