Why I am blocking hotmail.com

No protest against Microsoft which owns that service. Just the unfortunate fact that hotmail is apparently the conduit now for a DoS attack against us.
No, its not working.
But I am assuming that someone somewhere has managed to corrupt the inbound mail access at hotmail. Have discarded about 12000 mails in the last 12 hours. May start blocking hotmail at the firewall, not even let it traverse our network.