For Yahoo Email the Real Identity of the Email Id Owner is necessary. As anybody can enter a fake name, fake company, fake jobsite & create a fake Yahoo Email account & from it send us fake, advertising emails.
For knowing, checking Real Identity of Yahoo Email id user make any Identity Proof Compulsory - Like Driving License, Voter Card, Pan Card, Aadhar Card, Passport No when creating a Yahoo Email account.
As i get many spam, fake, advertising emails.