Because whoever programmed "it" wants a valid email address.
When Yahoo prompts you to "please enter a valid third-party email address" during sign-up, it means you need to provide an email address from another provider (like Gmail or Outlook) that Yahoo will use for account verification and recovery. This address should be active and accessible, as Yahoo may send a verification link to it. A valid third-party email ensures you can recover your account if you forget your password or lose access.
#1: Manually check each email address Head to email-checker.net. Enter the email address you want to verify. Verified email addresses will say 'OK', invalid email addresses will say 'Bad'
Any email address that you can prove you have ownership of (by clicking a confirmation link sent during registration) counts as a valid email address.
valid e-mail address means it has to be real and have: (your e-mail address here)@(website here).(ending here) To makesure it is an valid email address, you can go to http://www.fraudlabs.com/demomailboxvalidator.aspx to validate your email address.
no it means an active email
A valid email is an address at which you can be contacted, one that works. Most people have more than one email address so you put the address that is the most appropriate for the use intended.
Maybe becasue it is not a valid address.
roda1."i.ua
ys
yahoo.dodo@munchee.com
Satoru Iwata died in 2015, so no email address would be valid.