SPAM

Manage spam and mailing lists in Yahoo Mail | Yahoo Help - SLN28056

The downside of marking email as spam is that, theoretically, doing so alerts online security companies who will flag email from that sender as spam.  Future email from the sender will then be routed to your Spam folder without being available for filter rules.  But since Yahoo Mail filter rules don't provide a way to block email and only move email from that sender to another folder, filter rules for spam aren't effective anyway.

The only way to stop spam email is to unsubscribe from each individual sender.  For a reputable sender, that will stop all future email from them.  But, if the email is from a spammer, unsubscribe can verify they've found an active email account and could generate even more email.  Use caution with unsubscribe, but it can be effective when used properly.  I went from 40-60 spam emails per day to none on most days.  If you unsubscribe using the Yahoo Mail function, you will know Yahoo trusts that sender and you're trusting Yahoo.  See "Unsubscribe from sender" at the above website.  If you unsubscribe by clicking "Unsubscribe" in the email body, you're trusting that sender. 

  Caution: 100 spam emails received in 30 minutes are probably not all from reputable senders.