Besides the login email/phone, account recovery email/phone is an alternative method to receive verification code to reset your password. It can be very useful should you lose your phone or access to your login email.
Here's how to setup a recovery email or phone:
Visit the Login & Security tab on the HTC account website (http://account.htcvive.com), under the Security section, click Add account recovery phone. Follow the instruction to complete the process. You will receive a verification code email/text message during the setup to verify this email or phone is valid.