I received a spam mail into my inbox, from "Greek Squad" coming from address "thasnee0209@gmail.com" which I identified as spam by hovering over the sender. I immediately put into spam folder then set to block it via the "block address" procedure, where I have 381 of 500 blocked addresses. The procedure carries out the task, supposedly deleting email and blocking address; however, within 10 seconds, the email returns to spam folder. This occurs with quite a few other spam mails that have been picked up as spam. There appears to be an "advanced technology" being utilized by the spammers that isn't picked up and addressed by yahoo's mail system that should be addressed to prevent infiltration and reinforce Yahoo's prowess & effectiveness in email security