how to update email address in domain registration?

I need to port my domain name to new hosting service as I will no longer be using comcast.  That new provider needs to send an email to the address listed on the domain registration to get my authorization to transfer. That email address however is broken. Verizon killed the email account listed on the registration because it was so messed up and disfunctional.  I simply need to update that obsolete verizon email address on my registration to one that works.  I have been on the phone with comcast for almost four hours. Is this really that complicated? Can someone please help here?  Thank you.