Changing the Personal (Recovery) email

My xxx@comcast.net email address has an associated "Personal email", which I presume is used for authentication in case I lose my password to xxx@comcast.net.   Currently my personal email is from a former employer, and so I no longer have access to it.  My dilemma: when I attempt to update my "personal email" to something current, xfinity wants to authenticate me using the old "personal email (to which I no longer have access!).  My question: How can I change my "personal email" information?