Login SSH to your endian firewall and try
efw-upgrade -h show the help!
root@efw:~ # efw-upgrade -h Usage: /usr/local/bin/efw-upgrade Use -s to force channels setup and upgrade. Use -u to change the email address used to register. Use -h show this help.
Yeah! it easy way for change email, typing
efw-upgrade -u and enter new email address.