Log in to Online TurboTax. Near the bottom of the left column menu go into Intuit Account. Then go to the tab Sign In and Security. You can change the email address there, then you can verify it there with the link there. It may then send you a link to that new email address to verify it. Once verified for the Intuit Account purposes, close Online TurboTax. And then sign in again.
That might be enough to fix it. When you try to efile, if it still wants to send you a 6-digit email verification code, be sure the code is not ending up in your email's spam/junk folder. See this FAQ on some tips, which also includes info on how you can change the email address in your Account Settings, if you wish to use another email address.
FAQ: What if I'm having trouble with my filing verification code?
If that's not helpful, please phone Customer Support.
FAQ: What is the TurboTax phone number?
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632