How to Report a Message as Spam in Yahoo Mail
Yahoo Mail has spam filters, so most unsolicited messages are automatically placed in the Spam folder. Nonetheless, spam will occasionally make it to your inbox. To alert Yahoo Mail that junk mail that made it past the spam filter:
How to Report a Message as Spam in Basic Yahoo Mail
The process for reporting spam in Yahoo Mail Basic is the same, but the interface is a little different:
How to Report a Message as Spam in the Yahoo Mail App
You can report individual messages as spam while viewing them in the Yahoo Mail mobile app:
How to Report Spam From Another Yahoo Mail Account
If the spam is coming from another Yahoo Mail account, you can report the user directly by going to the Report Abuse or Spam on Yahoo page in your browser. Select report it to Yahoo directly and enter the requested information.