Block up to 500 email addresses or domains in Yahoo Mail to prevent spammers or other people from sending you unsolicited or unwanted emails. Emails from people that are on the Blocked Addresses list are deleted before reaching your account. The owners of the blocked email addresses or domains are not notified when you block them. You can, of course, remove specific email addresses or domains from the Blocked Addresses list at any time.
Log in to your Yahoo Mail account, mouse over the gear-shaped icon and select Settings from the menu to display the Settings dialog.
Select the Blocked Addresses tab to view and manage the Blocked Addresses list.
Type an email address into the Add an Address field and click the Block button to block it. To block an entire domain -- @sample.domain, for example -- type the domain into the Add an Address field and click Block.
To unblock specific email addresses or domains, select them from the list and click the Remove button. To select several addresses and domains, hold Ctrl and click each item.
Click Save to apply the changes and block or unblock the selected addresses and domains.