Hey @Aileen47! Once you add your new sending email, you'll receive a verification email to that address, and you need to click the link in that email in order to confirm it.
If you aren't receiving that verification link, please reach out to our team via help@convertkit.com100 (or the in-app messenger in your account) with a description of the issue and indicate which email address you're trying to verify. We'll take a look and help you get it confirmed!