Your old email settings should still work unless you already cancelled the service with Comcast.
If you already cancelled with Comcast I'd give them a call and ask if you can have the email account enabled for a day so you can copy out the email.
To avoid a repeat of this problem when you leave Verizon someday, consider
registering your own domain name.
I'm curious to know if Comcast can help enable the account and/or do an email restore in this case to get you access to the important email in case it's already been deleted.