In WordPress version 5.3 and above a new feature to verify admin email every six months is added. The purpose of this feature is to make sure that the admin email is valid and still being used for the site or not.
The admin email verification notice looks like in the image below.
Have you ever wondered why on earth we have to change the admin email address? This message might be annoying because you will see it every time you sign in to your dashboard. Your client might be annoyed by the notice.
You can completely stop showing this message. You have to add the code in your functions.php
add_filter( 'admin_email_check_interval', '__return_false' );
In this way, you can solve the annoying message of showing admin email verification.